The DLC will add five maps to Modern Warfare 2: Vacant and Strike from the first Modern Warfare, and Carnival, Trailer Park, and Fuel, which are all new. You can find more details on the three new maps here.
The Resurgence Map Pack will cost $15, same as the Stimulus Map Pack released back in April. And if interest in this map pack remains anything like it was for the Stimulus pack, then it'll probably sell really, really well.
Xbox 360 players have been able to buy it since June 3 thanks to a timed exclusivity deal, but now PlayStation 3 and PC gamers won't have to wait much longer for the latest Modern Warfare 2 map pack. Infinity Ward has announced that the Resurgence Map Pack will hit those platforms on July 6 in the U.S., and July 7 in Europe.

