Agreed, the power spent on doing native 4K would be better off spent on any number of other things IMO, but even just 60fps but lighting, materials, effects. Unfortunately, 4K is a sexy buzzword that the companies will use to sell their shiny new boxes.
Given the huge jump in CPU power, what I'm most hoping to see is exactly what I wanted to see from the 8th gen but which they failed to deliver; a big jump in simulation, interactivity, like BOTW's physics/chemistry stuff but x10.
BotW has very rudimentary and case by case physics.
What I'm hoping the most is first atempts at fully voxel based worlds with fine detail. Take a look at this tank (at around 3-4 seconds in):
Fully made of voxels - yet at first glance you wouldn't notice. This is just simple example, but imagine the whole game world built like that - whatever happens in that world, stays that way cause voxel octrees preserve all data. Trouble is, they need astonishing amoung of data, to be fine detailed, and need ways to traverse octree very fast.
Now I'm not sure about AMD's implementation of RT, but nVidia's RTX cards have additional hardware for traversing certain hierarchical structures, and it's my guess that this can be used to speed up octree traversal. In addition, voxel octrees make RT much easier to do from the get-go. This combined with SSDs gives me hope that sometime in next gen there will be at least some games that utilize this new potential and that are huge step up above standard "shiny, but non-interactive" polygons approach we've been stuck with for decades.