For VR, most of the major industry players are continuing to invest (and were never expecting it to go mainstream in the last few years), and the active user count is persistently going up. The absolute numbers are relatively low. But the cost, software, and hardware right now are all pretty terrible and rapidly being improved.
With a growing base and major cost/quality improvements on the horizon it probably has a fairly secure future as a niche gaming platform. I don't think the data is conclusive yet on whether VR is the Next Big Thing.
There's kind of a chicken-and-egg SW problem for new platforms. Most of the popular mobile apps were only developed because of a large existing base of networked devices. For iPhone 1.0, the killer app was probably the ability to use the desktop web. Is there anything VR could do for normal consumers, that doesn't require enormous software investment (before there's a market)?
People watching TV/movies on their phone/tablet is pretty common (in addition to the living room). It doesn't seem too out there that VR could become cheap/good/comfortable enough to be popular for that use case (watching 2D TV on a phone). It's only marginally less social if you're watching by yourself anyway, and could even feel more social depending how the virtual theater is set up. Maybe that's one pathway that could drive more mainstream adoption.
I think it's premature to mark VR as a fad just yet, at least before not-terrible mobile systems come out. There's not too many tech products I can think of that would be popular if they could only be used chained to a $1000 desktop PC.
Globally the numbers were ~15M in 1990, ~100M 1995, ~0.8B in 2000 (far from 100M in 2000).
And my point was, mobile exploded in 1990 and "kept expanding" (literally my words") -- there was like VR "a constant hype/disappointment cycle" (literally the thing I was responding to in this very thread).