Amazingly, I'm already starting work on DEC 2007. I've been talking with several notables[1] in the AD MVP community (Ulf, Dean, joe, Princess Horhay, Laura, Guido, etc) about putting on another pre-conf workshop. We' re pretty well settled on doing it around Longhorn Server AD. It will certainly include migration scenarios and read-only DCs, and "Lots of Other Cool Stuff"(tm). That is of course code for "we don't know what the heck else". But we'll figure out someting fun.
I've also been kicking around the iea of having a concurrent MIIS Gemini workshop to let people get their feet wet with declarative provisioning, entitlement support, and auditing. I mentioned it to Angela Mills (MIIS PUM), and she's going to look into how doable that will be. Developing....
[1] I'm not saying what they're notable for, however.