If your TV has a proper gaming mode with VRR, then the xbox will definitely take advantage of it.
I only have xbox One, but I still use the crap out of it on my 4k tv, which has all the gaming options I could ever want.
I may not play 4K xbox on it, but I do play many of my computer games in 4k... so I can appreciate a 4K tv.

Vizion ftw.