One of the campaigns is being developed by community member Matthew Lourdelet, creator of the popular Left 4 Dead map "2 Evil Eyes." Valve says Lourdelet's upcoming campaign called "Cold Stream" looks even more promising than 2 Evil Eyes, but the campaign isn't complete yet and Valve wants to get the rest of the community involved in the process.
A beta version of Cold Stream will be added to L4D2 in the coming weeks so PC and Mac users can begin testing. Valve wants gamers to share their feedback in a new forum section dedicated to the project. "We appreciate feedback from the entire community. This is an experiment for us, so please let us know what you think and what you would like to see in the DLC."
In addition to Cold Stream, Valve plans to port the three remaining L4D maps "Blood Harvest," "Dead Air" and "Death Toll" to L4D2. The original "No Mercy" campaign was added to L4D2 last October alongside "The Sacrifice" DLC. Valve hasn't announced a launch date for the upcoming map pack yet, but the developer says it won't come before Portal 2's mid-April release.