Well, could it? Of course it could.
https://www.youtube.com/watch?v=Ysh44rPC7ew
It has two big things going against it reaching or slightly surpassing PS2.
1. Lack of price cuts. Yes, Switch Lite has been available for years as a $200 USD option. But it is a Switch that cannot Switch and can still get JoyCon drift which is even worse in a dedicated handheld. I know inflation is a thing, so PS2 selling around the end of its life for $100 USD would be more than that today, but still cheap. Even when Switch 2 releases, there is a good chance Nintendo doesn't cut Switch's price. They'll probably just include a game or two with each Switch.
2. Switch 2 is set up to be a smash hit and likely launching March 2025 or before. Nintendo has not been in this good of a spot with a home console since the NES to SNES transition and on the handheld front the GBA to DS transition. I know Switch 2 hasn't been announced yet with a codename or unveiling, but it's unlikely Nintendo will make it another Wii U.
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
