liquidboy
Regular
Going forward, all three of Microsoft's operating systems will be lumped together into a single division, so as to share more technologies and components
Terry Myerson, current head of Windows Phone engineering, is now the head of the new Operating Systems Group at the company. Myerson is going to run engineering for the Windows, Windows Phone and Xbox operating systems. Anything that attaches directly to these OSes, such as Xbox Live, also reports into this new OS division. All of these OSes are currently running on a common "core" based on Windows NT
ref : Microsoft 3.0: A meaner, leaner devices and services machine?
There are economies of scale benefits when MS combines all it's coder resources into one division and code for ONE OS ... hence why a single OS that spans embedded/phone/tablet/desktop/server/cloud will mean MS don't waste valuable coding time on unique OS's anymore and MS will hopefully innovate faster
p.s. I would bet my last weeks salary that lots of the coding effort that went into Xbox One's architecture will make it into Threshold (Windows 10)