Is it though? Technology is progressing, sure. And it will find its use, but what are the datapoints or other clues that predicts that AR/VR will become mainstream? Not saying it will not, but what makes it, in your opinion, "inevitable"
My profesor at Uni predicted, that the next computer revolution will be "invisible computing". That firstly basically all everyday items will get chips inside (ie "Smart Things", it was way before Iphone &co) and then computing will bee something in the background. IDK, but it seems plausible to me and looks like we are moving into such future. VR is not compatible with that vision. Most ppl prefer real life to escapism. And event if you want to escape drugs are more fun and more addictive.
Solved but still not enough to make it seem reel. He said that natural light has 10x more dynamic range than best monitors available.
As to focal depth - in real world there is no "screen", your eyes (or perhaps brain:) can decide which what you want focus on and what can stay blurred. On screen everything is in focus, so you need to make fake blur. But you need to know what user is focusing on. So you need to read retina movements to guess. Sounds like complicated and hard problem to me.