"The HTC Vive offers the best consumer VR experience for now — but it needs better games" http://venturebeat.com/2016/04/05/the-htc-vive-offers-the-best-consumer-vr-experience-with-todays-technology/

HTC's connection with Valve Steam is not enough. HTC needs heavyweight support behind it - as heavy as Microsoft.

Microsoft has the games and console platforms on PC and Xbox. HTC has the hardware, but no games platform. They need each other badly.

Prediction: somehow the HTC Vive will become the Microsoft VR hardware. How they structure the deal remains to be seen but its a match made in heaven and solves a huge problem for both companies.