I've never used the Media Centre Extender stuff for my 360. Never seen the point when you could just run a DLNA server on your PC (like PS3MediaServer or TVersity) and stream using that.
So long as the Xbox One still supports DLNA and mp4 etc. like the 360, there will be no need for Media Centre Extender functions if all you want is streaming.
And getting back to the PS4
Hopefully Sony will listen to the fans and give the PS4 the same support the PS3 has!