All I can say is...
GOD NO!
Not in reference to the idea of another official setting, mind you. I'm actually in favor of that. I meant GOD NO don't let it be greyhawk. I mean, I get it. Lots of nostalgia. Old setting. But y'know what? Greyhawk might as well be any other generic fantasy as far as I'm concerned, and I'd wager that goes for anyone else who doesn't hold the same nostalgia as other old timers do.
I'd like to see something more exotic. A ressurection of Planescape would be ideal in my mind, but I'd also like to see Dark Sun, Al'Qadim or Spelljammer. Or pretty much anything else that's fantasy with a twist... If they do start publishing a new campaign setting, I'd bet dollars to cents it would be an entirely new one as opposed to a ressurection of an old franchise, though. Like I said, I'm fine with that as long as it's not just midieval europe with elves.
If I wanted plain vanilla fantasy (and I don't), I'd pick up Forgotten Realms.