Frankly a UI layer most likely wont be available on XBox One. You will be expected to roll your own, or use a 3rd party service like WinForms.
Also, I bet you just about any money Metro is dead as a dodo within 4 years, just like WPF before it.
I am so confused by this lol
Why would Microsoft allow people to use WinForms UI and not XAML lol? Do you have a source for this. Doing a quick search brought up some "Desktop dead" and "PC dead" links which was somewhat amusing
Personally I like all the XAML technologies but that's just me, I doubt VS would move onto WPF if it were dead or close to dying, besides what are the options for 'super quick' desktop development if it were.
No idea if metro will die in 4 years, but the next few years are going to be a lot of fun, so far ASP.NET MVC, DirectX, PC or Desktops in general and now metro are 'expected' to die, I don't really see any of them dying but lets wait and see.
On a serious note though, why is there very little info on Xbox One development, there is some crap about dev kits but nothing really informative