TBC seems the only way forward. Folks playing Classic sometimes can't even agree on what version of Classic they want (case in point: Alterac Valley), you'll never get them to agree on what changes should be made to Classic, and I doubt Blizzard is willing to open that can of worms.
Much easier to just release TBC in 2-3 years. And if it means I can eventually play a Wrath server, so much the better.