The console vendors are deathly allergic to GPL code and won't touch it with a ten foot pole, so even if the Xbox does move away from NT there's almost no chance of it moving to Linux. They'd sooner use a BSD like Sony does, or roll a custom kernel like Nintendo did.
This is pretty much what I expect. Windows will be "Linux" in a similar sense as Android is "Linux". Or BSD, or whatever. It won't necessarily be Linux specifically, but I expect it will be something.