Blizzard is expected to WOW TBC Gold launch something called "Wow Classic Season of Mastery" in a few weeks. The servers will provide an exciting new way to play traditional (no TBC content) but with some twists. These twists will include "leveling is faster" or "raid bosses can be harder to beat." If all you want to do is playing classic content , with no burning crusade things**, you should wait a couple weeks and make an avatar there
It's all based on the game you prefer, but Season of Mastery is a fantastic choice for those who enjoy the feeling of a fresh beginning and a whole new level. Many, if not all, of the Vanilla servers are essentially dead. They're mostly there to help players to keep their characters as an artifact at this point. TBC isn't a bad thing, but getting into a guild might be a little harder now that buy Burning Crusade Classic Gold people have already completed a significant amount of the way. I'm planning to dip into SoM when it comes out.