I don't normally like to publish rumors that I can't verify with at least a second source, but based on the corroborating evidence I received along with this tip, I do believe it's genuine. If not, then it's an internal attempt to get me to look silly publicly. :)
With that bit of morality out of the way, here goes.
Windows 8 will include a new tile-based user interface that's codenamed Mosh. Assuming this is true, I have to believe that this UI will be an alternative UI, and not a full replacement, or will appear only on low-end tablet-like devices aimed at the iPad. It sounds like something that will silence the critics who want the Windows Phone OS on a tablet.
Windows 8 will also include a new app model codenamed Jupiter that will target a new Windows Marketplace app store. The app store will provide access to new, Silverlight based "immersive" applications that are deployed as AppX packages (.appx). The Windows and Office teams are betting very heavily on this new app type, according to my source, and development has already begun using a beta version of Visual Studio 2012. These apps can be written in C#, Visual Basic, and even C++.
I've asked around for corroboration on these items but have turned up nothing yet. So please take this with the grain of salt intended. Again, based on other information I've received from this source, I do believe it to be the real thing. But there's no way to be sure. And I want that to be clear.
I'm curious to see if any of this information is discussed in tonight's Steve Ballmer CES keynote of course. Stay tuned.