A report from CNET shed some light on a potential VR headset X-Box was working on. The device would have been a competitor to the PSVR, but not on the level of the Oculus or HTC Vive. The project was put on hold, as X-Box supposedly decided not to proceed until they could produce something that would be more than just a competitor. They wanted something that would have been unique.
Source: Game Spot