We've heard the idea of "classic servers" passed around before -- some players believe that things were better way back at level 60, when Molten Core was the beginning of the endgame, Tier 3 was as high as things got, and you had to coordinate a whole 40 man raid (shudder) just to pick up a few epics. Blizzard has already said no -- they think it would be trouble to run two different versions of the game at a time, and you have to wonder if they have the capability, as much as the game has changed, to run an old server anyway.
But that hasn't kept some players from continuing to ask -- someone has even put together a whole site called, cleverly, "Level 60 Love," designed to convince Blizzard to re-offer the vanilla game again. They've got a mission statement, a FAQ and forums, and even a few ways to "help" out (though you could question how signing a petition helps, but we guess every little bit counts).
It's not too farfetched -- as they point out, Dark Age of Camelot once hosted "classic" servers, and the idea of legacy raiding is something that's already happening in game. But of course it's up to Blizzard -- even if they feel the demand is there (and it sounds like it would take a lot of demand), they might just see it as a sign that they need to justify the newer content and do more things like the recruit-a-friend and quicker leveling.