I made a thread about this before, but I am wholly convinced there is a way to allow for a display of 120 but gameplay logic still tied to the 60.
I just want shiny... I just want smooth.
No doubt it is theoretically possible. I made a post about that before, too, but recently I discovered that USF4 on PC can actually be set to run at lower than 60 FPS. If you run the game in 50hz mode, it runs full speed at 50 FPS. I even tried locking the frames to 30, still full speed, even though it was choppier. It just doesn't allow for greater than 60 and your game speed will slow down if you drop frames mid-match. I'm guessing the logic is set at the start of the match and doesn't allow for variance during gameplay. Still that brings up the possibility that USF4 might already have the inner workings of a variable frame rate system in place or atleast something that calculates the game state separately from the rendered frames since the frame data on moves have to stay intact.
I think KI might be running at higher rate of logic on XB1 because they said the game runs at 90 FPS but caps off to 60. It will be interesting to see if KI allows for higher FPS on PC.