Battle for Undercity removed in Cataclysm
If you haven't done the extended series of quests in the Dragonblight that lead up to the Wrathgate cinematic yet, first off, I don't understand why. Get up there and do that. However (and more importantly), if you haven't done that quest line all the way to its satisfying, lore-filled conclusion, The Battle For The Undercity, by the time the pre-Cataclysm patch drops, you might not be able to.
In response to a forum thread started by Cedrickt on the beta forums, Valnorth stated that the Dragonblight quest line ends at the Wrathgate cinematic on the beta. As yet, there's no further information. We don't know if there's any intention to add in entirely new quests, but I expect not; trying to gibe Garrosh as Warchief with the events of Wrathgate (to which much of his policy toward Sylvanas is a direct response) would be very difficult indeed.
Go play it while you can. It's a lot of fun.
World of Warcraft: Cataclysm will destroy Azeroth as we know it. Nothing will be the same. In WoW.com's Guide to Cataclysm, you can find out everything you need to know about WoW's third expansion. From goblins and worgen to mastery and guild changes, it's all there for your cataclysmic enjoyment.
