New application model in Windows 8
The new tile-based interface is slated to appear similar to what is currently available on Windows Phone 7 and will only be available on tablet like devices. Jupiter is not a replacement, but an alternative to ARM. This should be a cost-cutting measure for Microsoft and should allow for faster propagation of new lower-level features throughout different form-factors supported by Windows NT and Windows CE.
Codenamed "Jupiter", Windows NT everywhere, Silverlight/.Net everywhere!