My impression of pessimism came from his skepticism that Moore's law would continue long enough to get them to where they really wanted to be on mobile VR, his struggles with latency probably making cloud rendering a poor experience for most, recognition that they were already at the ceiling of their heat and power budget, his belief that foveated rendering was not going to save the day, his recognition that the lenses were now a limiting factor vs the screen for image quality and that other lens designs would be fragile and suboptimal in a shipping product.
I didn't mean to say that I thought he was pessimistic about VR overall, just that he didn't seem to think there were any large gains in hardware quality coming soon and it was down to the software to make full use of what was there.