If Switch is considered Gen 9, it probably will have a notably bigger lifetime unit total than PS5 or Xbox Series. But if the Switch successor (which is probably still 2.5-3.5 years out) is considered Gen 9 and Switch is considered Gen 8, I'm not so sure.
The fact that Nintendo has a hybrid and launched it mid-life in comparison to the PS4 and Xbox One makes it really tricky to pin Switch down to any generation of hardware. As a home console, it's more around Gen 8 (a weak Gen 8, but stronger than Gen 7). But as a handheld, it is pretty much Gen 9. It's a huge leap over the 3DS/New 3DS and PS Vita.
Lifetime Sales Predictions
Switch: 151 million (was 73, then 96, then 113 million, then 125 million, then 144 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 57 million (was 60 million, then 67 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
