Windows 10 for Xbox One will be known as One Core and will be coming to Xbox One this month for preview members who opt in and November for everyone else.
Discussing One Core on Larry “Major Nelson” Hyrb talks in depth on his Podcast from the 34 minute mark onwards. Director of Program Management, Xbox and Windows Platform, Mike Ybarra spoke with Major Nelson about Windows 10 for the console. One Core is a customized version of Windows 10 made specifically for the Xbox One platform and has some tasks running up to 50% faster than they currently do.
The main objective of the opt-in will be focused to the most active preview members and aims to make the new OS “super fast and responsive”.
— Mike Ybarra (@XboxQwik) September 11, 2015