That's one of the things that does bug me about the idea. Different people have different ideas about when the game was in its best state. The other question is where do you go from there? Do you freeze the game in that decided state? Do you re-introduce the patches overtime from there? Come up with original content just for that branch? (In order from least to most labor intensive). The game would get pretty stale after a while if it was frozen in some previous state with no updates.I can see a few problems with this.
First, what do we define as classic, and how do we go about doing so?
Frankly I think the best part of the game was never any particular feature or patch but rather the community. I think a lot of people are just "done" after having played the same game for several years, i think that's really more of what it is than any particular thing in the game making people leave.
As I've mentioned before though, I wouldn't necessarily be opposed to them trying this if it didn't compromise the current game for those enjoying it.