Valve planning to release Dead Air "early"

Announced earlier, Valve want's players to test the Cold Steam maps.

Which could not be at a better time, currently Left 4 Dead 2 is on sale for $4.99 on Steam.

Valve wants 20,000 players to get the Stream Crosser achievement (Survive a campaign of Cold Steam on any difficulty) by the end of this upcoming Sunday.

If 20,000 achievements are unlocked on time, Valve will release Dead Air with the upcoming Cold Stream DLC, instead of at a later date.