Whenever a new technology shows up, all OEMs usually compete with each other with a standard of their own. Its good in a way, because it makes a better product, but at the end, everyone converges to make things compatible. The story is same for VR as well.
Thanks to Khronos Group, they have already initiated a project “OpenXR” which plans to standardize the way applications interact with the hardware i.e. AR and VR. This group has all major players from the VR industry including Steam, AMD, Nokia, Huawei, Google and so on. This will make sure that even though companies keep innovating in their own way, they still can go cross-platform.
Microsoft is the latest addition to this group to make sure their Mixed Reality headsets can work cross-platform one day. Right now the devices only work with Windows 10 Fall Creators Update, but when this gets implemented, you might be able to play Steam games directly or maybe even with the phones when the next version of MR arrives.
Microsoft has just started with MR, well technically they had been doing it since Kinect, and then HoloLens, but getting on board for consumers is pretty new. But getting into OpenXR is a great move and strengthens the fact that they want to do something in this space, and are serious about it.