Amazon (who paid nearly $1 billion for Twitch) and Google really believe there is a real future watching people play games, but one real challenge seems to be the VR integration.
Personally, I'm not sure this will be a big deal, since the VR content itself should be more interesting. And if you care, the lower half of the face will still be visible anyway.
What might be cool tho, is being able to stream the complete VR sphere so the viewers could look behind and around and just be within the streamers control.
But even going forward I'd posit that it'll only occupy a (small) niche. Consoles are going to have trouble supporting it -- not due to their never being "powerful enough" (as consoles will of course get more powerful over successive generations) but rather simply due to the power disparity needed to render a game normally vs VR. Developers aren't going to want to release a game at vastly lower detail settings for VR than for general TV-based consumption (and they won't forgo the TV-based audience, except perhaps for niche lower-budget VR-only titles).
Moreover, some of the most popularly streamed titles (anything not first person -- League of Legends, Hearthstone, etc.) are simply not suitable for VR.
But it's true that VR is an immersive experience which I can't vicariously participate in the same way I can watch someone playing Hearthstone now. In many ways VR games are likely to remain largely unsuitable for streaming.
I dunno, the classic Civilization style could benefit quite a bit from it. Imagine having a virtual giant globe that you can arbitrarily turn and zoom as the main interface.
Even the limited number of platformers with a third-person view on the Oculus Rift hardware are quite successful, since the false depth perception helps with fine control.
If you're looking for something more interactive, replay videos already exist for a wide variety of games, with the ability to change perspectives. Simply mapping the full system state to a local engine for rendering will allow you to view any perspective of the VR game character. You move your head, the perspective changes, but the 'body' of your character is still in the streamer's control.
VR itself is a bit different though, as not everyone will have Rift/etc, so either you are streaming to a very limited audience, or there has to be a way of capturing the footage before it's transformed, and even then, it's just one eye, so the viewers are missing stuff.
Streamers will make sacrifices for their audience. If the technology isn't available to stream VR well then they won't do it.
What would be really cool is a game that supports streaming to YouTube 360, where it records a view similar to what the Jump camera rig does in real life.