Hoping to rally the community and squeeze in some beta testing, Valve has called for gamers to complete Left 4 Dead 2's "Dead Air" campaign in versus mode and unlock the new "Connecting Fight" achievement (we believe it's a typo for "Connecting Flight"). If 60,000 people earn the achievement, the company promises release another campaign, "Blood Harvest." As you're probably aware, No Mercy (added last October), Dead Air, Blood Harvest and Death Toll are the original L4D maps.
If this sounds familiar, it's because Valve used a similar tactic to launch Dead Air a month ago. The company asked gamers to hammer on the upcoming community map, Cold Stream -- though the bar was set much lower. The developer only demanded that 20,000 people earn the "Stream Crosser" achievement for surviving the campaign on any difficulty in any mode (instead of just versus), and that feat only took some 24 hours to shatter.
It's unclear if you have to escape Dead Air alive or if you just have to reach the final level and play until the credits roll, but the latter seems most likely. The achievement specifically says "play a versus game on Dead Air from start to finish" instead of specifically saying you must "survive" the match as with similar achievements for other campaigns. If you've earned the achievement, feel free to clarify what its requirements are in the comments.
Regardless, by tripling the required number of successful completions and limiting them to versus, the new challenge should be more difficult. Last time, Valve only gave gamers about four days to complete the task and there was a defined release day for the DLC (July 22). There are no certainties this time. Players don't have a strict deadline to finish and Blood Harvest will simply be added the next weekday after the 60,000 mark is breached.