Megapixel displays & Foveated rendering
tl,dr: Some companies (including Google) have announced soon-to-be available (2018) very-high resolution VR/AR displays. To deliver on these, two problems need to be overcome - not enough memory bandwidth or GPU compute available)(to be solved with foveated rendering techniques) which then adds on the problem of gaze tracking to control the foveated rendering. Turns out that both of these are understood, solvable problems. Coming soon to many HMDs.