Re-Birth of a fantasy setting to be announced at Gen Con by WotC
Apparently at the Gen Con Keynote address this thursday night at 7pm at Gen Con, Wizards of the Coast will be revealing which fantasy setting they'll be bringing back, presumably for DnD Next.
While Greyhawk makes the most sense, I don't think Dragonlance or Planescape should be considered out of the running. I'd personally like to see Blackmoor or the Known World. While I love Ravenloft, I'm not sure how well it functions as a full setting.