Hold onto your hats, folks: Activision has announced that in its first week of availability, the third multiplayer map pack for Call of Duty: World at War sold more than a million units on the Xbox 360 and PS3 combined. Including the previous two map packs, Call of Duty: World at War multiplayer add-ons have sold 6.5 million units combined.

“The support and enthusiasm from the Call of Duty: World at War online community is tremendous,”said Mark Lamia, studio head of Treyarch in a press release.  ”The team is appreciative that so many players from around the world have continued to enjoy the game and all of the downloadable content that we have produced.”

You have to wonder if they’ll continue to make these for the forseeable future. I don’t see why not–the downloadable content itself is becoming as big of a business than most retail releases.