Perhaps DL this year and Dark Sun next year -- but they're running out of major well-known settings if we discard ones where significant aspects are now included in the extended-core (Planescape via MotP and DMG2, Spelljammer via Adventurer's Vault, Ravenloft via Domains of Dread, etc). What's left? Mystara?
Mystara is a possibility, but the way Chris Perkins talked on a podcast (the Tome Show?), it definitely did not sound like Mystara was even on the radar.
We know that the setting has an A in it, so that rules out Birthright. And from what Chris Perkins said, it sounds like Birthright may not make a comeback. Likewise, I doubt it's Council of Wyrms.
The two big contenders seem to be Dragonlance and Dark Sun. My money is on Dark Sun. With the release of psionics next year, and the re-release of the Prism Pentad, there will be no greater time for Dark Sun to make its 4th edition appearance.
Another good possibility is Greyhawk. With the passing of Gygax and Arneson, it would be a good time to capitalize on the nostalgia factor and to do a major reboot.
Other possibilities, which are much less likely, include:
1. Taladas - Dragonlance's other continent, which includes 3 instances of the letter A
2. Maztica - Never popular, and wiped out in the Realms anyway.
3. Al-Qadim - Arabian Adventures!
4. Kara-Tur - Only if presented as the home of Oriental Adventures.
5. Tale of the Comet - Unlikely, but boy would it be fun!
6. Ghostwalk - Possibly, but I don't think it got that great of a reception.
7. Blackmoor - I don't think WotC has the rights to this.
I've cracked Logan's code!!!
LOL!