Well i think it will be 1080p in handheld and maybe upscaled 4K in console mode to be close to a PS4 pro. I mean they can see people will buy the Switch at a high price so maybe they can make it 50$ more for the next one if they want to boost it a little and put it into specs so it gets a bit more third party support since we know now it is working well with Nintendo.

It will depend, if they make a Switch pro and really milk it, the console still has no price cut so it can really live atleast 3 more years imo.