I've been piecing together information from various sources regarding the newly demoed Windows 8 Tablet UI and I'm getting the distinct impression that it's very similar and perhaps derived from the Media Center UI. Remember that the Zune UI is purported to be the basis for Windows Phone 7 UI. But what was the basis for the Zune UI? It goes back to the Metro project which also spawned Media Center.
It makes sense as the Media Center UI was designed from the ground up for the alternate input input method provided by a remote but could still be used with the keyboard and mouse. Adding touch should be a no brainer. That combined with the existing support for Media Center extensions which where based on HTML and script, I think we're just looking at another Media Center type UI facade -- another shell if you will.