I'm hoping many games have a 1440p120 option, as 4k resolution cannot be resolved by the human eye and most people's viewing distances but 60 -> 120 fps is a very noticeable change.
I think that could happen, especially on Xbox as they are making a song and dance about 120fps and every bit of input latency would count there. But with those techniques I mentioned, dynamic 4K120 with VRR could even be a thing. It's a shame there are such things as development times and budgets that scupper ambitions. Interesting times ahead for sure.