Work on Left 4 Dead 2's fanmade Cold Stream campaign continues and Valve is reaching out to the community to help weed out bugs and glitches. To reward players for their efforts, Valve will release Left 4 Dead's Dead Air campaign for Left 4 Dead 2 on July 22 if 20,000 players can earn the "Stream Crosser" achievement by the end of July 10.
How do you earn "Stream Crosser"? Just complete Cold Stream on any difficulty. Simple as it sounds, Cold Stream's finale is very difficult to overcome due to the constant streams of common Infected coming from everywhere. You may want to switch to an easier difficulty to earn the achievement.
Update: Over 60,000 players met Valve's challenge, guaranteeing an early delivery of Dead Air for Left 4 Dead 2. Valve is aiming to get Dead Air released as soon as possible but assures the campaign will be available by July 22 at the latest.
Valve also revealed there is a new version of Dark Carnival's finale and general changes to other finales in the works. They will be tested on the PC version for a period before being released for Xbox 360 players.