You are seeing a higher PPI push not just for VR (although it def benefits from it), but for the next evolution of displays moving to quantum dot and HDR (not to be confused with camera HDR).I was think more along the lines of a device similar to a phone.
I mean why make phones with 4K displays just so it can be used for VR. That is such a niche market. Why make a phone with a 4K display that will only appeal to a very very small amount of the buying public. when they could make a device very similar to a phone that would be cheaper because all it would need is the 4K display and ram and processing power. So it might be in the sub $350 range.
The general smartphone buying public would benefit more from better battery life. Not a 4K display that is targeted at a small niche who would use it for VR. Anyway...just my thoughts.
The ultimate goal is to get a 3d display with perfect clarity without the need for glasses. And after watching 4k content on my TV, I'd say that the goal is within a year or 2 time.