Probably gonna play it safe like DS -> 3DS, Switch -> Switch 2 or whatever they call it. I suppose maybe it will do more AR stuff (like that physical Mario Kart remote controlled toy/game) but nothing you haven't seen on mobile phones (still, more affordable than some flagship models for sure).
Would be nice if the joycons have some sort of accurate motion tracking tech bringing back Wii-like controls (but more like current VR controls in scheme/setup) and hopefully accurate enough to enable lightgun style games to work properly this time, not like on an actual Wii with its limitations.