Seems like some people are vastly under-predicting Switch's sales. We're in the midst of another high 20 millions year and there are a slew of huge games coming out next year, it should be around 105 million (or slightly higher) end of this year. Switch will likely be passing 130 million by end of March 2023, and there are people on here predicting a lifetime total of around 130 million lol.
All you gotta do is add the numbers up. Switch this year so far has outsold last year, and should have a bigger holiday season this year so even though it's slowing down now it should sell around what it did last year (27m+). That should put it at least at 105m this year. It'll start to drop next year sure, but minimum it's gonna be 125m by end of 2022. Then we've got all of 2023, worst case scenario with Switch dropping hard would be 140 million end of 2023. In this worst case scenario in which Switch is dropping hard in 2023 that'll force Nintendo's hand to release successor in Spring 2024, so Switch would be a bit shy of 150m by end of 2024 with it being replaced earlier that year.
A few more years to sell a little bit would probably put it at right around DS or PS2 sales...and that's just about the WORST case scenario! Anyone talking about under 140m sales is living in an alternate reality, seriously. Just look at the numbers, 130m is a joke, 140m is a joke, 150m is a low prediction, 160-170m is very very doable.