It seems that Cortana is already appearing on some users’ Xbox One consoles.
The Windows 10 update for Xbox One is not set for release until November, and with it will come a number of updates and improvements. Notably this update will include a new store, faster and more efficient access to the gaming experience and OneGuide for media content. Cortana, on the other hand, was not expected to make her debut until early 2016. However, a few Reddit users are reporting that the digital assistant is already available on Xbox One for those who are currently testing the New Xbox One Experience (NXOE) preview.
Watch this,Using Cortana on the New Xbox One Experience