There are a lot of rumuors about Windows running everywhere and looks like it comes true. We know Windows 8 is for PC/Tablet and it would be a surpise if its runing on the next Surface.

WP8 is going NT kernel

http://www.zdnet.com/blog/microsoft/could-and-should-microsoft-change-the-heart-of-windows-phone/11164

http://hal2020.com/2011/11/04/windows-phone-8-and-windows-8-cousins-or-siblings/

XBox is the next

http://www.g4tv.com/thefeed/blog/post/718132/next-gen-xbox-rumors-points-towards-windows-9-and-arm-functionality-codename-loop/

Here my 2 cents on this topic in the conext of WPF/e (aka Silverlight). http://janhannemann.wordpress.com/2011/11/07/the-shift-from-wpfe-to-windowse/