I think with the todays Nintendo direct and the fact that MK8 will be supported until late 2023, we can assume that Switch will be long enough the main Nintendo system to be able to beat PS2 and NDS. Nintendo will not launch a Switch2 before late 2024/early 2025. Otherwise the MarioKart DLC timing would make no sense.
Imagine new tracks are keep on coming, but before the end of the new tracks there are information about Switch 2 already... That would make absolutely no sense.
So I am pretty sure now, as long as no absolutely crazy unforeseeable events are happening, Switch WILL outsell PS2 and NDS!