The upcoming patch 3.02 looks like it has a formal name now -- "Echoes of Doom," according to the EU site -- and players have wondered for a while whether Blizzard is going to bring back the Scourge Invasion event. This was an event that went live with the introduction of the original 40-man Naxxramas in patch 1.11 and saw Scourge troops appear all over Azeroth and even within major cities. It was one of Blizzard's early experiments programming world content that could be directly affected by players (in a roundabout way you can trace the underlying philosophy behind phasing to the success of events like these), and was a huge hit that's left players inquiring on the likelihood of its reappearance ever since.
As a player who started after Burning Crusade launched, I have to admit I would love the chance to see this, if for no other reason than having a shot at getting my main the rather good-looking Tabard of the Argent Dawn. But, cool tabard or not, the event is pretty thematically consistent with the content being released in Wrath of the Lich King, and the 3.02 patch is expressly meant to transition players into the expansion as seamlessly as possible. You could argue that Blizzard's never going to get a more opportune or relevant time to marshal the undead NPC's, but you could counter by pointing out that redeploying content originally meant to be a unique event diminishes its impact a tad. If it were re-programmed with additional exapansion-related content? Maybe, although I get the feeling the developers may be somewhat occupied at the moment. Either way, is there any obligation on Blizzard's part to try to re-run old content for the benefit of newer players?