The next version of Windows, code-named Longhorn has incredible possibilties.
The desktop, as you know it, dies with Longhorn. Instead, it will be a fully composited desktop. Or, to put it another way, it will have the same kind of performance one would expect from a full screen Direct3D game. That means all kinds of things will become possible.
But will Microsoft keep the door open for third parties to extend and customize Windows? With all this new power, the potential for incredible innovation in the Windows market by third party developers is immense. But only if Microsoft also adds in hooks for third parties to get in there and do things to the system that no one in Redmond has considered.
This article at JoeUser.com talks about this in more depth and has a few never before seen screenshots of Longhorn in action.