On the forums of Steam, a user who goes by the name of Disapproval has claimed to have visited the studios Valve and have also met Jay Pinkerton and Erik Wolpaw, the key figures of the company. You said that the two would have been very kind, so as to have also responded to several questions about Portal 2, mainly on the game's first DLC will be released by summer.

Disapproval was confirmed that the DLC in question will offer a whole new co-op campaign, complete with a brand new story and set the Aperture Science Lab In the unsettling, with GLaDOS still at the helm of strange experiments in which we will be subjected. The content will also add the online leaderboards to compare our results with those of other players, while the question of whether the DLC will also include new single-player levels, Disapproval said he's not sure why Pinkerton and Wolpaw have spoken only of the co-op .

Finally, again according to the words of the user of steam, Valve would not have mentioned a specific date for the first release of this add-on but would be limited simply to say that will be released "very soon". In short, at this point we just have to wait for the start of Gamescom Cologne and hope for an official announcement.