My view is the Switch was a trial run for Nintendo for the real Switch 2 that will follow. They are already asking devs about 4K games, and to me that would imply using DLSS.

They will go hard and make a new Switch 2 as soon as it is practicable for them to have undocked mode at 1080p 30fps/60fps. This will then be scald to 4K

Personally I hope the Switch last another say 3 years then in 4 years time we may even have a switch model that has ray tracing built in. 

I do agree about that early on when the console was fresh out, but some did still so this spring, where it doesn't made any sense whatsoever anymore.

I still see Youtube videos saying stuff like, "Do you think Switch can outsell the Wii?"  People on Youtube aren't necessarily following the data as closely as people on this site.

I can't say I see many people on here predicting total sales to be less than 100m... I think most know that it's a given at this point (barring asteroid strikes or deadly covid-21)

Those that do perhaps just don't understand sales momentum, the Switch is technically behind the Wii in launch aligned sales after all and the Wii only just topped 100m. Maybe that makes things look bad for Switch, but that's just a snapshot in time not looking at the bigger picture, Wii may be currently ahead launch aligned but it's average non-holiday sales months were down to less that half of it's peak year.
Momentum is important, the Wii sales exploded from launch but peaked in it's 2nd year and was already on the decline in early 2009. Switch is still accelerating coming up to the end of 4th year.

It's fairly easy to predict a few months in advance, +75 million is the minimum it will be at by the end of December (78m more likely). If from January onwards it has the rapidest sales decline of any console/handheld in recent history it would still break 110 million easily, and a more modest Wii like decline (which was still very fast) would see it topping 120 million.

Sony is better about keeping momentum than Nintendo. Sony puts a few big blockbuster games on their console leading up to the release of their new one. Nintendo generally lets its systems quietly just die. You might get a cross-gen game but not always. Switch sales are peak momentum now and while Switch will hit 100M. PS4 will just sell more since Switch is likley peak now and in 2022 leading into maybe 2023 new releases will slow to a crawl from Nintendo.

One word to answer your question: Wii

At this point it is certain that Switch will pass the 100 million milestone, but to catch up with the PS4, let alone the DS and PS2 it remains to be seen. Imo, the Switch will eventually surpass the PS4.

Denial

Oh no doubt (at least with hardware, as Nintendo 1st party software often just sells for the life of the system), but that doesn't mean Switch has no momentum, the sales will not hit a wall even if Nintendo stops supporting it with games.

Huh? This is exactly what the OP is saying haha. "probably" will reach 100m?? It will probably reach 100m NEXT YEAR! It should end next year right around 100m. And the Switch 2 will still be multiple years away at that point. 120m is like the guaranteed bottom at this point. Like, if Switch died HARD and very soon it would still sell 120 million at this point. Again, this is what the OP is talking about, why do people still say stuff like this?

Maybe it's the talk of the new Switch model and some people seem to get confused and for some reason think it's a Switch 2 and not just another Switch model that is coming out soon. Switch 2 is yeeeaaaarrs away, 3-4 years away at this point. And in just over one year from now Switch should hit 100m. That's a hell of a lot of time to sell above 100m before the Switch is even replaced.

If Nintendo replaces Switch a little on the early side, like say holiday 2023, Switch should be looking at over 130m lifetime sales. If they replace it at what I think would be the perfect time, Spring 2024, it'll probably end up around 140 million. If they keep putting out good first party games for it in 2024 and don't replace it until holiday 2024 and the price is all cheap by then, then it could hit 150 million (49+29+24+17+14+9+5+2+1 = 150).

Yours is just a theory of many. There's no evidence for anything you just said. At least I was basing my assumptions off history.

Wii had 6 years before WiiU came out. In case of Switch that would be March 2023. That's in 2 1/2 years. Certainly not within your 3-4 years estimation. On top of that I proved how badly the Wii sold in 2012, the year WiiU launched. Only 5 million sales. WiiU was announced 1 1/2 years before it came out. Using the same time spans, Switch 2 will be announced in Fall 2021. That means Switch would have only 12 months of strong sales left and then could drop off completely in 2022.

Btw. the successor to N64 was released after 5 years and the successor to Gamecube was released after 5 years. Finally, the successor to WiiU 4 1/2 years later. Yet you expect 6 1/2 years to 7 1/2 years for Switch.