Microsoft has announced that it will be bringing in cross buy support between the Xbox One and Windows 10 devices. It’ll work the same as the PlayStation cross buy promotion, where if you purchase a game on one of the systems you’ll have access to the other version at no extra cost. The announcement came during Microsoft’s GDC conference.
At the moment two games have been confirmed for this cross buy initiative, with those being PinballFX and the MOBA Gigantic. The latter will also support cross platform play. Developers won’t have to offer their games on the service, but it will be open to all who wish to use it.
Source: Wario64 Twitter/PCGamesN

Starman
Cross buy between 360 & x1 would be nice.
JesseDeya
How do they intend to distribute the Windows version? Through the app store?
beeje13
Yes, so no you won’t get a Steam copy through cross-buy. Well, I would think not.
You could always use the steam overlay over a Games For Windows game back in the day, so I’d imagine you can do the same with this.