8k x 8k per eye at 120Hz is 64x more pixels at 1/3rd increase in frequency ~= 85x more processing power. Making the (maybe faulty) assumption of doubling processing power every 2 years and that current setup is processor limited, this sort of processing power is ~13 years away.
Same computation but with 4k x 4k per eye predicts ~9 years of progress needed.
I guess I misspoke about being 1920x1080 which is a "2K" screen split in two. An 8K screen split in two would be ~4000x4000 per eye which is still 16x as many pixels as I said, plus the 33% increase in frame rate which I didn't include which matches your second one. Although with how embarrasingly parallel it is, I don't think it's as far off as it seems. Especially considering that it's the previous generation graphics cards that can handle current day VR fine so we're 1-2 years into the 9 years we have to wait, and with so many pixels anti-aliasing can probably be turned off completely. You could probably build something today that could do it, it just would be very expensive and I don't think 8K panels at cell-phone size exist yet.
8k x 8k per eye at 120Hz is 64x more pixels at 1/3rd increase in frequency ~= 85x more processing power. Making the (maybe faulty) assumption of doubling processing power every 2 years and that current setup is processor limited, this sort of processing power is ~13 years away.
Same computation but with 4k x 4k per eye predicts ~9 years of progress needed.