@tnp Dark Sun would require conversion of the Psionic rules, which I haven't seen yet. It would be fun to see, though.
To put in whatever my 2 cp is worth...
Dragonlance & Forgotten Realms: Popular, lots of lore already known by the playerbase, but needs to be rolled back to before everything went to poop (pre-Second Cataclysm for DL; pre 1372 for FR as mentioned above)
Ravenloft: Possible, with the recent rise of non-WoD horror games. Probably would have to have 1 Staff member dedicated to playing a Lord and running Events in their realm.
Greyhawk: Doable and not as already over-exposed as Dragonlance & Forgotten Realms
Mystara: The old Basic D&D setting; well documented with lots of published lore/splat.
Planescape: Widely popular and adaptable, centralized 'city' to use as a main gathering point for PC's
Spelljammer: Yes, yes, yes, yes, yes......Set up the Rock of Braal as a centerpoint of the game similar to Sigil/Waterdeep/Greyhawk. Plus ship combat and boarding actions. And abandoned Dwarven Fortresses. And, and, and....
Birthright: This would be awesome. The setting has a built in Political/Trade/Intrigue mechanism, a nice Mass Combat mini-game system, and combines a solid Lords & Ladies RP setting with classic D&D Adventuring. Also adds a bit more epicness (Bloodlines, Realm Magic) to D&D.
Original Setting: I don't think players would be too opposed, but learning the lore of a new setting can be a bit time consuming, IMO.