The 3DS was dropped like a rock, it was completely replaced. 

Obviously anyone saying 2022 Switch 2 has very different ideas about how Switch 2 will function within the market. As we can see looking at the launch of Series X, all of its first party games will also be playable on Xbox One. No one is expecting the Switch to be replaced in 2022. 

No it wasn't it was still supported even after NS came out the were people here complaining about Nintendo still making games for it while NS was out it's only in the pass year where it has been dropped and that's 9 years into its life mind you, the platform was still very much active a year or so after the NS released as Nintendo last released a first party game for it in October 2018 with Luigi's Mansion.

I am still a believer for a collapse of the sales after Christmas 2020 (the next in 6 months).
Then in 2021 a new console is presented, and it comes out in 2022.
It is not the announcement which makes collapse the sales in my scenario, but the Switch will simply run out of interest.

Oh yeah, this is true! Well then lets say that the vast majority Nintendo's flagship titles skipped the 3DS from when the Switch was launched.

Zelda BOTW, Mario Odyssey, Mario Kart 8 Delux, Splatoon 2, Arms, Fire Emblem Warriors, Mario Rabbids etc

No one expecting a Switch 2 in 2022 is expecting Nintendo to suddenly release 8 big exclusives on it from their main franchises that prematurely kill the Switch. It will be a soft transition from Nintendo's. 

Oh I have made a screenshoot and saved this...

I will show you this again in a year or two.

Not me.

We live in a dumb world because people have no memory, they can be continuously fooled.

First off, no, 3DS wasn't dropped like a rock, but for the sake of argument... so what?  The point is that it was Nintendo's money maker, didn't live up to their expectations and it still got six years of life and dev support before their next console.  Switch's life before its successor won't be shorter than the 3DS.

Second, if you think that "No one is expecting the Switch to be replaced in 2022" then you haven't been paying attention.  There are plenty of people who erroneously believe that Nintendo will release a new, more powerful Switch to combat the arrival of the new consoles.  Will there be a redesign of the current Switch?  Inevitably.  But will there be an all new console that supports an all new library?  Not any time soon.  And yes, when Switch 2 does arrive it will be backwards compatible just like Series X/One, obviously.

2024. As long as games not developed on NS first will be developed for PS4 and XBOne too, there will be little or no difficulty at all porting them to NS too, but when most games not made for NS first will be developed for consoles with 12GB to 16GB RAM on entry level models, and moreover developed for recent SSD's, porting them to a 4GB RAM machine with slower and very much smaller internal storage (and even slower card based expansion), will become very hard or impossible, so while 1st and 3rd party exclusives and multiplats developed on NS first could be fine forever, to keep good relationships with as many 3rd parties as possible, Ninty will need to release a new machine when they need it. Scalable engines, and devs increasing max GPU usage faster than they increase CPU usage, mean that Ninty will still be able to keep power lower, competing, home-only consoles, and graphics RAM or the part of unified RAM used for graphics won't need to be as big as in competitors, but main RAMused by the CPU will need to be almost as big as in competitors (some savings will be possible with a more frugal OS and having to cache smaller textures, but a total 66% saving, as it will be keeping a 4GB machine compared to 12GB minimum competitors, will be impossible), and internal storage too will need to be much larger and faster, although smaller textures will allow some savings in size and speed.
Anyhow, considering competitors use Zen 2 CPU cores, NS will be able to get the necessary power from latest or almost latest 2024 tech ARM or Zen CPU cores while keeping power consumption within hybrid console limits (battery tech improvements will help increasing these limits, making things even easier).
So we can expect NS2 to be very powerful without killing battery autonomy and costing at launch no more than NS.
This anyhow doesn't mean sudden death for NS in 2024, as long as devs want it will still receive new games (and while the most HW demanding games won't be portable, the huge user base NS will have then will make desirable for 3rd parties to port any game that can be ported), and as long as Ninty wants it will be produced, just like DS and 3DS before, and until NS2 price will drop enough, ther will still be a market for NS1 too. NS lifecycle could easily reach and surpass 10 years, even with NS2 coming in its 7th year.

Why a new console in 2022 would necessarily mean a brutal STOP for the Switch ? They can keep selling the Switch cheap at a decent pace until 2030 while there is a new gen system as main product.
They can unlock some more GPU from the current Switch, but this will never be enough to really push farther the technical limit of acceptable ports the Switch can handle. Even from 2017 to 2020, the Switch received nothing serious from Capcom and Square. I don't think that repeating the Nintendo's IP again and again on a limited hardware will be enough to keep the competition after 2022. Decreasing the price to 250$ (or offering Mario Kart 8 with the console), will offer a good boost, but for how long...

lol, I am one of those people. What I'm saying is that people's concepts of console succession and commercial success are very rigid. Times are changing. 

If you see the Switch as the 3DS' successor, that was a hard reset where Switch immediately received flagship Nintendo games that were not available on the 3DS. A lot of them. When people talk about a Switch 2 in 2022, many of us are not talking about a platform which arrives and forces the OG Switch out of the market right away with a whole bunch of exclusive Nintendo experiences.

Also Arbirary comparison don't make the best sense here, the 3DS may never reach the Gameboy Advance 81m figure but the GBA was replaced a lot quicker (4years). 

Remember the new3DS/DSi? These received exclusive software, and were weird late gen updates. Instead of doing a weird refresh or simply having a Switch Pro, I think Nintendo will just have a new Switch which will eventually transition into its own platform. Nintendo has found their mojo now and I think will more aggressively keep people in their echosystem and expand their online services with iterative hardware & soft generational leaps. No more starting from zero every 6 years.

This is an extremely safe business direction, the main counter argument is that it hasn't been done before in the game space but we can see MS moving towards this. The other thing is people are more obsessed by unit sales of individual platforms then they are about the actual stability and share value of Nintendo the company.

I think the Switch 2's release will not be based on the current Switch's sales. The Switch will inevitably be in decline in 2022, it's just a matter of when Nintendo feel the technology is right to offer a generational leap because I don't think Switch 2 will have any USP compared to Switch 1. And just as the Tegra X1 was released 2 years prior to the actual Switch, a Switch 2 in 2022 will not actually be any weaker than if the platform was released in 2024. A hard generational transition forces you to launch at a more accessible price since your entire business is leaning towards the new platform. A soft transition gives room for the Switch 2 to start at a premium price and live next to the more mass market $199-249 Switch for casuals, budget house holds and late adopters.