[alkonaut]

Between e.g. central and west US you'd have a physical ping of ~10ms so 20 round trip just based on the speed of light (i.e. very hard to get rid of). Meanwhile the input lag you want is one or two frames so on the same order. But this lag is additive, when the game receives the new state it has to compute and render the world, the display has its lag before it shows up etc. So the new frame has to start computing as soon as the input is registered in order to hit reasonable input lag.

Predicting 2-3 frames should't beyond what we can do at least roughly. Especially for some important inputs such as turning in first person view it should basically just start moving the screen. I belive John Carmack tried some kind of rotational prediction (Not based on AI) for Oculus.