It could do it with streaming, but even like that it wouldn't be really do it since most places wouldn't have internet for it.
On HW basically impossible outside of indie games with simple graphics, even XSX or very powerfull PC will struggle with most games at 4k120fps.
Nvidia DLSS doesn't require the internet. It can be done in hardware.
As for the thread, for a Switch 2, DLSS 2.0/3.0 would absolutely be a huge game changer. Switch 2 could render at native resolutions even significantly lower than the current Switch has to and achieve an end image quality comparable or even better than 900p-1080p undocked and 1800p-full 4K docked.
If effectively reduces the number of pixels the Switch 2 has to render by 1/4th, and who knows with DLSS 3.0 eventually that could get even better.