John Lam has let part of the cat out of the bag - the "new" thing he alluded to a while back appears to be linked to Microsoft Silverlight, what seems on the face of things to be a rebrand of WPF/E, an attempt at a Flash killer.
The programming details will have to wait for Mix 07, but for now the buzz should start. It's ironic that a matter of days after Paul Graham declared Microsoft "dead like IBM" that something like this should be announced.
It will be interesting to see how this fits into web development with Adobe's Apollo. Adobe has played a masterful first hand by making Apollo open source. It will be interesting to see how Microsoft responds.
The good news is there is a CTP for download, so for those of us who won't get to Mix, there is room to dig around.