Bethesda already have knowlege of VR, with the beginning of Oculus, right? They should make a team and continue from were they were left. Doom studio ID could make a great exclusive for them, if they do believe in this. But I can see that go the same way as their Holo lens efforts. Nowhere because they don't really believe in it yet.
Yeah there's an abundance of both hardware and software VR knowledge in everything Microsoft, especially via WMR, they never stopped working and collaborating with other players in the scene. They've f.ex. coworked on other brand's VR hardware, f.ex. HP's brilliant Reverb G2 4K VR headset which is a MS, Valve and HP collaboration. Another good example is that one of the best VR experiences in the market right now can be found in Microsoft's Flight Simulator. There's nothing else quite like it, it's a tour de force in VR.
The main reason MS hasn't released VR hardware for Xbox is because it's infamously a highly volatile VR market right now with little to no money in it. And with the pace technology goes headsets could be outdated before the consoles themselves are.. But what MS and everyone else knows is that VR will have its mainstream gold rush with plenty of money to go around, they just doesn't know exactly when that's gonna happen.
A sidenote: When it comes to Hololens it was alway a conceptual AR PR device meant to target R&D in businesses first and foremost (I know because we had two of them in our own lab at work), I can guarantee that no one in MS expected a 4000 dollar flawed AR device to become popular among gamers. They put it in gaming conferences to make a buzz surrounding their brands, to make it seem that they are very much still in it when it comes to AR/VR (which is true) .