Old thread dug up, interesting.
The PS2 will remain on its throne. As will the DS. The best any platform (even the Switch) can hope for is third place. If I'm being more generous to Nintendo, Switch could possibly sell 140-145 million units.
Switch 2 isn't coming out really soon, I would think. March 2023 at the earliest, and it will probably be after that. Once that happens, the Switch can't logically sell 30 million or more once its replacement is out. PS2 sold about 40 million units after the PS3 launched. That won't happen with the Switch. The Switch 2 launch will not be as much of a blunder as the PS3.
Lifetime Sales Predictions
Switch: 156 million (was 73, then 96, then 113 million, then 125 million, then 144 million, then 151 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 48 million (was 60 million, then 67 million, then 57 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
