Auction house in Cataclysm?

since orgimmar is getting a big overhall, I imagine they will keep the AH there to generate more traffice through the city

cant find a source, but I believe dalaran will remain as-is

As happens with expansions, Northrend will be as much a deserted, empty place as Outlands is now.

Also, I believe Blizz is sticking with the "AHs belong in Azeroth, nowhere else" philosophy.

With the release of the new expansion all the level 80 traffic that currently runs through Dalaran will return to the old world to begin questing to 85. Just as Shattrath is a ghost town today, Dalaran will be after the 4.0 release. The only reason to return there will be for the portals and for leveling 68-78.

With all traffic returning to the main continents, the capital cities will once again be heavily populated (and likely just as laggy as Dalaran is now) and will continue to be the primary trade hubs for the realms.

Both Orgimmar and Stormwind are receiving new Auction Houses and Banks, but they are essentially in the same place. There are no plans to place new auction houses elsewhere in the world.