I actually think a starter town in the DMG will be awesome. Right now the only ones I can think of them having are Threshold, Keep on the Borderlands, or Hommlett. I supposed they could have a "town" called Greyhawk, but I bet they'll save that for their "starter city" in the PHB 2

.
I think a 4e Temple of Elemental Evil would rock, hardcore. Given the new take on demons and Tharizdun, the story behind the dungeon would just be so much better IMO. And to me, ToEE is probably THE iconic dungeon. To do it justice they should make it a massive work, like Goodman Games's Castle Whiterock (actually, IMO, WotC should just contract the job out to Goodman Games

).