Despite coming out with the Xbox ONE, Microsoft is pushing away from gaming, believe it or not. They're focusing more on Social media these days and things like that, so they aren't exactly bothered to try and put their hand in the market. The RIFT is improving quite a lot as more and more time passes, and it'll eventually have console support. Sony on the other hand is entirely focused on gaming still so that's why they are giving it a shot;
Ultimately, I don't see the Sony Headset going anywhere since it'll most likely be much more expensive then the RIFT and won't offer nearly as much support. Most likely being restricted to only the PS4 (MAYBE PS3) and only on the games SONY deems acceptable to support it. While the RIFT just needs a few calibrations to work with most games out now.
Either way, we'll see where things go, but I don't think Microsoft is going to even bother.