130M

137.8 million

Look at the weekly sales charts for the last couple years. You'll see that this is true every single year, sales drop in April/May compare to January through March. And it's not just the case for Nintendo, but Sony and Microsoft, too.

Plus, last Spring and Summer got massively boosted due to the 1-2 punch of Animal Crossing and the pandemic. If the sales weren't down by now despite the wait for the OLED and the lack of high-profile releases until Metroid, then we would be on track for 35M+ this year with everything that comes this fall.

130-135M, but only because in some years Ninty will have to replace it with the next gen, mid-life beefed-up models won't be enough anymore. Had the base model higher specs, particularly RAM size, it could sell 150M, maybe even more.

that depends, if the mid gen refresh DLSS's up they wouldn't need to.

We must split the problem: 

1) Mid gen refresh usually can run more smoothly and nicely anything that's developed for that gen, and if new games stress just consoles' graphics section, scalable engines will ensure there won't be problems even in multiplats
2) But games must run also on entry level models. This isn't a problem for exclusives, neither is in the case above, point 1, new games that just want more graphics power for their higher settings, but it is for multiplats that need more CPU power and larger RAM, in this case entry level models (not just NS ones, but XS too, only PS5 entry level saves costs on other things, but offers the same APU power and RAM size) will eventually limit what devs can do if they want their games to be multiplat. Anyway this worst case won't happen immediately: cross-gen titles that must run on last gen too won't ever have any problem, while current gen-only ones will start having problems in a few years, but not now, and only CPU and RAM heavy titles will be a problem

But all this just in theory, as surely Ninty designed NS HW taking into account its desired lifecycle since the beginning, and general cost cutting and slowing down  in all sectors of economy due to the pandemic most probably will give NS and the whole current gen at least one more year of life. When entry level NS CPU power and RAM size will start becoming a problem, Ninty will be ready.

Probably around 135M - 140M

It depends entirely on not if the cliff hits, but when it does. PS5 and even XBOX Series sales are really rising so for the first time in a long time Nintendo will even be competing with MS.

I'm late to this, but here's how I see it.

Right now if Switch from now on were to decline at a steady and average pace for a successful Nintendo console it'll be on pace to sell around 145 Million Units lifetime, which currently seems like the most realistic scenario, and the 40% plurality of the voters in this poll would agree with that.

In a slightly more optimistic case, the Switch would sell between 150-160M Units putting it around PS2 & DS sales. However, the Switch selling this much isn't as optimistic as some people want to make it out to be. It's certainly within the Switch's reach to surpass 150 Million sold. The current pace the Switch is at right now is to sell 145 Million, which is only 5 Million away from 150 Million so it is easily within the Switch's reach to get over 150M. It really all depends on how long Nintendo wants to extend the lifespan with the Switch, which is currently somewhat vague at this time. Nintendo has stated multiple times they want to extend the lifecycle beyond the typical console lifecycle and said they're around the midpoint in its life 3.5 years after Switch launched, which would mean Switch 2 will release 2024. However, actions speak louder than words and Nintendo has had a history of not staying consistent to what they say. So we have to wait & see regarding how long the Switch will last. However, if the Switch gets really good pricecuts and Nintendo doesn't immediately drop the Switch after the successor and markets it as a budget system, 150M would be more likely than not but we need to see what happens. Nintendo might not be willing to do crazy price cuts on the Switch and rather sell each one at a profit even if it means fewer sales, kinda like what Sony did with the PS4.
However, I do think there is a good chance the Switch 1 remains supported after the Switch 2 since Nintendo wouldn't want to bank too much on the Switch 2 if its a failure especially since they only have one platform now, so the Switch will be a safety net kinda like how the 3DS was to the Switch. But we'll need to wait and see. However, 150M is certainly within the Switch's reach based on the pace its going and not as super optimistic as people want to make it out to be.

However, the slightly more pessimistic side would be anywhere between 130-140M, its certainly possible that the Switch fall just short of 140M if Nintendo decides to kill the Switch early, but most likely scenario is anywhere between 140-150 at this time. 150-160 being slightly optimistic while 130-140 being slightly pessimistic.

However, anything less than 130 is extremely pessimistic, almost considered an extreme prediction as Nintendo would need to kill off the Switch at an unprecedented rate starting now to fall short of 130M units.

Anything over 170 is extremely optimistic and 160M is also very optimistic.

Thinking the Switch successor will release in spring 2023 is illogical. Typically Nintendo unveils the existence of their next console & their codename for it around 1.5-3 years before it actually releases. The Switch was unveiled 2 years before it released as "NX". The Wii U was unveiled around 2 years before release, Wii 2.5 years before release. Gamecube was 2.5 years, N64 was 3 years, ect.... If Nintendo is releasing a successor in Spring 2023 we should already be hearing about it by now from Nintendo, or at the very least some type of rumors or leaks that its on the horizon, we haven't seen any of that and Nintendo hasn't even hinted at new hardware on the horizon at all in their investor meetings and its now late 2021, only 1.5 years before your predicted switch successor is forecasted to release. Its illogical to think its coming that early when we haven't heard shit about it thus far, we should at least have seen hints or rumors of it by now but nothing is pointing to a Switch successor in spring 2023 right now.

Plus, the Switch is forecasted to sell around 25 Million this fiscal year alone ending March 2022. Why in the world would Nintendo want to immediately drop a system that is still selling at historic pace with historic profit without one price cut yet by releasing a successor as early as Spring 2023. It just doesn't make sense at all from a business standpoint. 

Also, we still got a multitude of AAA games forecasted to release for Switch in 2022, we got Splatoon 3, Zelda BOTW 2, new 3D Kirby, Bayonetta 3, Mario+Rabbids sequel, Pokemon Arceus, and likely more unannounced titles that are on the horizon for Switch in 2022. If 2022 was the Switch's last year before the successor releases no way it would get this much support in its final year, typically Nintendo consoles in their final year  rarely have a multitude of AAA game releases. Typically the final year of Nintendo consoles consist of either remasters or budget filler titles like Mario tennis or something like that, Nintendo doesn't invest  into so many AAA games in the consoles final year, as typically Nintendo would rather shift those games onto the successor and within its launch window to give the successor momentum to start. It just doesn't make sense for Nintendo to release this many big games for Switch if 2022 were its final year.

Plus, it doesn't help that there's still a major chip shortage as Nintendo is struggling enough to supply the regular Switch right now. To Switch manufacturing to a successor that isn't guaranteed to be a success from the Switch which is widely successful is risky from a business side.

All this shows that a spring 2023 release for Switch 2 is highly unlikely as the earliest I could see a Switch 2 releasing is holiday 2023, but the more likely scenario is 2024 or 2025 right now. Which would mean that the Switcg selling over 130 and around 140-150 shouldn't be a problem.