[jayd16]

Seems like Microsoft would be the obvious choice. They just bought Xamarin, they're finally in a good spot with regards to C#'s growing cross platform viability and they're actually a game publisher.

I don't really know why MS would bother unless not doing so would risk a Unity collapse and a loss of a lot of C# development.

[Impossible]

Many of Microsoft Window Mixed Reality\Hololens apps are made in Unity also, so it makes sense there.