I think the opposite…TBC will be even bigger than Classic. The viability of a lot of specs is greatly enhanced. You get some cool new spells. Blood Elves and Draenei. Flying is FUN. Great raids, good dungeons. A fair amount of people like Arena. There’s a lot of polish that wasn’t in Classic…and yet it still retained the community aspect (no cross-realm dungeon finder, no crz). Homogenization hadn’t run rampant yet, so class identity is still great.
Personally, I’m in the camp waiting for TBC. I just ask Blizzard to provide at least a couple of brand new servers where everyone starts from scratch.