Pixel density high enough for acceptable text is already possible, just prohibitively expensive. See Varjo's headsets, for example - at the center of the display they have 70 pixels-per-degree (for comparison the Quest 2 has about 20).
> high enough for acceptable text is already possible
I don't understand this. I code and read in VR almost every day. With proper aliasing, it's extremely acceptable as is. Font characters per degree has to be increased, of course, but Quest 2 is about the same as a 720p virtual monitor.
I actually think pixel density is one of the easier battle to win. Getting a cheap, lightweight, strain-free device to users is the real requirement.
For now, I can't handle more than ~30 mins with any VR/MR/AR device, but if I can actually wear one for several hours and be productive using one - I will be convinced we've turned the corner on this tech.