You also have to think about the latency, and if I'm not mistaken they already want 60 FPS as the default, and I know Carmack wants 120 FPS eventually, because framerate is apparently a lot more important in that kind of virtual environment, because it's more obvious when you have dropped frames. So 120 FPS is probably "ideal", but not practical yet (the screens aren't there either).
Add to that 2x or 4x (4k) the resolution, and you're going to need really powerful hardware and very fast cables. HDMI 2.0 and Thunderbolt 2.0 barely support 4k @ 60 FPS, but I suppose that's getting pretty close. There are probably other bottlenecks, though.
