Not to sound rude but you clearly have no idea of what your talking about. If you could just brute force your way to 60 fps that would certainly be the more common "mode" in the enhanced games. And not higher rez which is the case.
How many open world games do we have running at 60 fps this generation? Far Cry, GTA, RDR, Assassin's creed, Horizon, Whatch Dogs, Just Cause, The Division etc all run at 30 fps for a reason. MGSV is an exception but it also features far less dense environments. Expecting Rage 2 to run at 4K/60 like Doom is 100% unreasonable. It was never gonna happen. In fact, I would be really impressed if the game manage to hold a steady 60 fps at 1080p.
I feel sorry for every one that will skip this game du to the resolution. What a strange thing to do considering there is far more to image quality than just rez.