I think 2 mil. on average in the 3 non-holidays quarter in FY2025 is sportive. If we take FY2023 as a baseline an assume that sales in FY2025 are roughly down 50% compared to FY2023 we have the following result:

FY2023:
Q1: 3.43
Q2: 3.25
Q3: 8.23
Q4: 3.06
FY: 17.97

FY2025:
Q1: 1.72
Q2: 1.63
Q3: 4.12
Q4: 1.53
FY: 9.00

The difference is that you reach the 9 mil. (for LTD of ~ 150 mil.) by end of calendar year 2024 whereas I by end of FY2025. Will see who's closer (I hope you).

A) A new system is definitely coming.  That doesn't mean it is coming next year.

B) Nintendo is not Sony.  I see a lot of people on forums making the mistake of thinking that Nintendo is just going to follow what Sony has done.  Except Nintendo is known for doing their own thing and not following Sony.  This particularly makes sense now, because Nintendo is the market leader and not Sony.

Nintendo supported the 3DS for a couple of years after the Switch released.  Expect them to do the same thing with the Switch, since this is how Nintendo behaves when they only have 2 systems to support during a console transition period.

If dev kits are available, and especially available outside Japan, then a new system is coming next year. There's no way Nintendo is giving out dev kits especially to non-Japanese dev houses for a system that is 2+ years out. 

Nintendo may treat the Switch like the 3DS, but they may also treat it like the DS, they killed the DS off quickly because they wanted those people to buy a 3DS instead. 

Understand to Nintendo if someone buys a Switch 2 instead of a Switch that's a WIN in Nintendo's book. You need to stop characterizing that as some of loss of something somehow. A Switch 2 *is* a Switch 1, but also a Switch 2. It ensures that Nintendo has that customer locked into their software ecosystem and will be able to buy all their software releases for the coming 6-7 years and not just older titles, and it ensures the Switch 2 builds a userbase that much faster. Both of these are beneficial to Nintendo, they don't hurt Nintendo at all. 

What is left in the tank to give a sales boost?

Conservatively:

- Super Mario Bros. Wonder (definitely will give some boost after seeing how Zelda: TOTK boosted more than expected), also probably a new Special Edition with Super Mario Bros. Wonder motives, maybe even Switch Lite Special Editions

- New Pokémon game(s) (even if no new mainline game comes to the Switch 1, every spin-off still will move some units)

- Metroid Prime 4 (Metroid was never a big seller but this game is hyped up now for so many years and I think it really can move some units in the die-hard shooter community who play on PS, Xbox and PC and didn't see a reason to by a Switch so far. Most of them will probably buy it on Switch 2 but still it will add up to some sold units)

- Mario spin-offs (Super Mario RPG and Peach game are already announced, I expect also another Mario Party game and definitely another Olympic game as next year the Olympic games are in Paris (France is a Nintendo Land), maybe even a new non-Olympic Mario Sports Mix/Superstars will release at the tail end of the Switch lifecycle as a joint-release also for Switch 2. A new Mario & Luigi could be aother joint-release. Those Mario spin-offs will not move alot of units but still add up to something.

- Long awaited fan favourites (Mother 3, F-Zero, Wave Race, 1080°, Star Fox, Golden Sun, Nintendogs/cats, etc. Again, they will not move a lot of units but still add up even if the majority of them will be bought for Switch 2)

- 3rd party games (Indie games will not stop comming to the Switch, also some interesting retail games will still come and contribute a little bit to unit salse)

Best case scenario (incl. all the above mentioned):

- Switch 2 is not a successor but Nintendo will count it to the same generation as Switch 1 (like GBC was same generation as original GB)
- If the above is not true then a Switch Pro will still come out before the release of Switch 2 (unlikely, but hey, we talk about best case scenario here)
- Imporved SKU's: lighter, more comfortable, better design, sexier, more storage, etc. could come for all versions: basic Switch, Switch Lite and Switch OLED but if a new SKU comes, probably for OLED
- Even more Sepcial Editions
- Attractive bundles (thinking about Super Mario Bros. Wonder)
- Price cuts for all SKU's (would have a huge effect on Easter European countries and rest of world)
- Price cuts of software (i.e. Nintendo Selects)
- Switch 2 will not release before holidays 2025
- Heavy support of Switch 1 even after release of Switch 2
- 3rd party exclusive suprise hit nobody expected (sometimes it happens that a simple kind of stupid game catches fire in social media and everybody needs to have it)
- Switch 1 becomes a hit in China

The reason Nintendo killed off the DS so quickly was because the 3DS got off to a really bad start and they had to change plans on the fly and go all in on it to get it up and running. Its launch lineup was poor and the 3D gimmick was a flop - nobody cared about it. There's a reason why they had to slash its price from $250 to $170 in just 5 months.

The same thing will not, or rather, SHOULD NOT, happen to Switch 2.

To the best of my knowledge and unless I'm mistaken, that was the only point in Nintendo's history where they had to sell hardware at a loss. Because they had no choice but to take the L for a while in order to get the 3DS off the ground and running - And it came at the cost of the DS' final years/last legs because it's successor was now at the same price range as the DSi models, which effectively killed their legs. If things had gone Nintendo's way, the 3DS would have been successful from the jump, they would've kept its price at $250 and the DS would have gone on selling at a lower, but steadier rate and had a more gradual decline - Which is EXACTLY what they want for the Switch -> Switch 2 transition.

Based on Nintendo's own 15M forecast for this FY. I had the Switch's quarter sales somewhere along these lines: 3.00M, 3.00M, 6.00M, 3.00M.
Well, it's already ahead by 0.91M, so it's off too a great start. If Super Mario Bros Wonder lives up to expectations, it should have no problems matching or exceeding the 6M figure I have predicted for this holiday season and I'd even expect that game's momentum to carry it into a good chunk of Q4 so that it's just enough combined w/ whatever they have planned for that quarter to meet or exceed THAT 3M number as well. My only concern is THIS quarter - As great as Pikmin 4 is doing software sales wise, is that really enough to maintain the Switch's momentum coming off of Tears of the Kingdom and carry it over to Wonder? We shall see in early November.

As far as Switch 2 is concerned, I think it's a forgone conclusion that it's coming next year. My guess would be a September/October 2024 launch. With the next 3D Mario game as a launch title or during the holiday season 1-2 months later assuming they don't have another highly anticipated title slated as a cross-gen launch title just like how Breath of the Wild was for the Wii U/Switch transition... COUGHPrime4COUGH.
And just as Rol said, I too expect a pretty beefy launch price - $400, maybe even $450. With software selling for $70 across the board. And that's not even considering how much the new controllers or joycons may cost. The price of the new accessories, games, and the system itself will make it so that it would need a very strong launch lineup in order to get it off the ground running. Even then, I would imagine that the vast majority of early adopters will be the avid, diehard Nintendo fans and dedicated gamers like us who will be onboard from the get go and are just waiting for the right games/lineup or perhaps that ONE killer app to tip us over the edge.

However, the casual fans and parents will probably hold off on making such a steep investment until either cheaper models come along, and/or inflation finally slows down and wages catch up so that investment won't be so steep anymore. Until then, they'll be perfectly content on getting the much cheaper Switch 1 w/ a far more robust library for their kids. ESPECIALLY w/ the knowledge that all those Switch 1 games will all be playable on Switch 2 when they finally do make that jump (Yes, I fully expect Switch 2 to be backwards compatible.)

While that's going on, Switch 1 should see a slow, steady, and gradual decline. One closer to the 3DS than the DS which will allow for better legs that just might carry it to that mythical 160M+ finish line.

Assuming the rest of my FY forecast remains the same, the remainder of Switch's life cycle could go something like this:

FY 2024: 16 million (141.62M)
FY 2025: 10 million (151.62M)
FY 2026: 5 million (156.62M)
FY 2027: 2.5 million (159.12M)
FY 2028+: 0.88 million+ (160 million+)

The 3DS wasn't the only time Nintendo sold hardware at a loss. The GC was sold at a loss for a brief time after its price got slashed to $99.

The Wii U was even worse than the 3DS, because it was sold at a loss from the get-go and it never reached a level of mass production that could get the hardware to break even.

I feel like agreeing. Yes, Nintendo has a history of killing off their old hardware in favor of their new hardware. But there are signs of change. The most important is, how much they now talk about the disruption a new gen creates. That points towards backwards compability, that they want to keep digital purchases from Switch on Switch 2 and I feel also like they want to keep Switch around for a while as a lower-priced entry console. That would've multiple advantages. Lower price reduces a hurdle for some people, so they can reach new demographics. As these new owners still would buy some games Nintendo could make money while they have to deal with the lower install base of the new hardware. If Switch 2 is backward compatible this also means these new Switch owners are building a library they could take to the new device if they jump ship later, even years later. And it could start people on being addicted on Nintendo games. I think keeping the Switch around for a time with the successor on the market, at lower price and produced in low volumes might be beneficial for Nintendo.

Nintendo was, at a point, the most egregious of the console manufacturers to kill the previous Gen when the next came along. But the 3DS thing you’ve pointed out, and other things brought up by them, make it likely that they’ve changed their direction.

I think it’s both good for business and consumers alike if Switch support continues for years to come. There are people who have families and multiple Switch units in the household. It can get rather expensive if you need to upgrade everything day 1 because Switch 1 is being killed off. It’s a bad experience, and the console industry isn’t just competing against itself anymore - no matter how many righteous anti-mobile people there are in console fandom, mobile is massive competition, as is PC. Parents don’t have to worry about support being cut off from old mobile devices and PC for a very long time. A major factor for growth for Nintendo would be to make their devices always seem like the best option for families as well as older console gamers. Focusing on both is not just possible, but also beneficial.

That said, my opinion of what Nintendo should do is little indication of what they will do. I’ve been wrong about Nintendo before, they’re not even close to as predictable as Sony. And I say that as a fan of Nintendo for over 35 years, and one with only a trivial interest in Sony consoles since the Vita.

While they phased 3DS out slowly, they also pretty much had to bet on it for a while because that was their only cash cow in the console market leading up to the Switch, which they didn't know how well it would do.

The rate at which a platform holder wants to 'kill off' their previous system is determined by many factors.
Obviously PS4 support stuck arround longer than planned because of the chip shortage for example.

A drop in price for a system largely depends on manufacturing costs, which in turn is affected by the rate of mass production for the components.
If for example Switch 1 is the only system that requiers certain components, they won't drop in price as much as they would if other popular devices also used those same components. The higher the demand and mass production, the more it drives down cost.

Backwards compatibility is also an interesting subject to think about. While making cross gen games will be no sweat off Nintendo's back, third party developers will probably generally want to leave Switch 1 behind as soon as possible if there's a successor, because porting to Switch 2 will likely be notably less expensive in general. At least until there are no more games being made for PS4. At which point they may be back in a similar situation again, depending on what measures they have taken to alleviate this. Things like DLSS will help, etc.