Eh.. the Tegra X2 is afaik not the gigantic leap in capabilities that would make this a sensible move. Most games, especially the non-indie ones, would need to heavily upscale to 4K in portable mode and it's doubtful any could run in native 4K in stationary, in some devs might be able to enable checkerboarding 4K for a nicer image quality.
VR would need a heavily reduced fidelity to be useable even at sub-native res, or they'd need to integrate 240+Hz eyetracking to cut rendering demands with foveated rendering (only the fraction of the screen the users eyes are focussed on is displayed in full res) making it probably a quite expensive device.
I like the input. It is possible it might not be true 4k but pseudo UHD. It could also be an up conversion of sorts. Mainly to provide a high enough resolution for a decent VR experience. If Nintendo has something in mind, they will figure out how to do it effectively. It likely won’t be conventional, as we all have seen from all of their consoles. I believe while Playstation 5 might be more VR focused out the gate, Nintendo still could be the one to bring VR to the masses with more convenient, affordable, and family friendly options.