I would be surprised if they didn't, I know it's easy to be flippant but during the fucked up times of 5 hour Whitemane queues people let their subs lapse never to return. So to pretend like it doesn't matter is foolish. Also the dead servers never get replenished, they are seen as ghost towns to be avoided at all cost. It's not a surprise that attendance and people in general quit overtime without new content but they lost 10's of thousands of subs at the very least not because of the game but because they were to lazy to get in front of these things.
TBC will bring a new influx of players, for a period of time layers will have to come back on the mega servers and the dead servers will remain dead shitholes. Blizzard could get in front of these things and should for the health of the playerbase and too keep rolling in the subs, but when they only care about quarter earnings and not long term health of their products I guess you could just turn a blind eye to these kind of issues.