If the market is about 10 - 20 million users, that's plenty to support developers and future development. The investors who made big bets probably aren't going to see much of a return on that money, but that's okay. VC money is probably bad for the sector in the long run anyway.

Don't forget that the current generation of VR hardware has roots back to a Kickstarter project. Billions of dollars are investment aren't needed.