Brian Harry published a must-read roadmap which should give you a good idea of what's coming in future releases of Team Foundation Server. There's a LOT of great stuff in there which should whet your appetite about what their team has been hard at work on.
The first comment Brian received on his post pretty much sums up my reaction as well:
"(with big grin on face) I keep telling everyone in the company that not only is TFS very cool right now, but that "this is only the beginning". I'm very happy to see you guys really gaining momemtum following the v1 release. Keep it up!!!
I am hoping to conduct a series of Channel 9 interviews with the Team Foundation Server team in the coming weeks to drill into this roadmap a bit more... stay tuned.