You're wrong, bandwidth on different interfaces (PC<->HMD, HMD<->panels, ...) is very much one of the hard parts.
Re:Nvidia GeForce GTX 1080 Ti
by Dylan16807 on Wednesday March 01, 2017 @04:25PM
(#13768568)
It may be hard in an objective sense, but it already exists. It's not the hard part of making a high-resolution VR headset because you can buy chips that do it for you.
A single displayport 1.3 cable, supported by all recent GPUs, can push 4K at over 120Hz. Screens that use such data rates already exist too.
And cancel the rest of my comment, I just found out there already are early 4K VR headsets.
https://vrworld.com/2016/11/10/hands-on-review-pimax-4k-vr-h...
http://360rumors.blogspot.com/2017/01/ces-2017-hands-on-with...
This particular device uses HDMI 1.4 and has a terrible framerate, but it's close to doing the right thing.