Valve originally announced the first piece of Portal 2 downloadable content for a summer release back in April, and now it has confirmed that the DLC will actually be released in mid-September. Doug Lombardi, the marketing director at Valve, stated that it’s "still technically summer".
Portal 2 "DLC #1" (as it’s being called) will be free for all platforms and include new test chambers, leaderboards, challenge modes for both single and multiplayer, and more.
We will keep you updated for when a set release date is announced.
[Kotaku]
