Windows 8! Apparently, a PowerPoint presentation has been leaked. It shows a prototype-y design of a computer (Maybe MS will actually build their own computer?). The stuff it mentions looks too good. This would give the impression that it will be like Windows Phone 7, with very few computers being able to support it, and them needing to be very powerful.
Read a lot of the details here: http://msftkitchen.com/2010/06/windows-8-plans-leaked-numerous-details-revealed.html