Valve announces the rumored update for Team Fortress 2 will indeed be the Mann vs. Machine expansion, and as surmised, will add a co-op mode to the free-to-play game when it goes live on Wednesday:

Valve, creators of bestselling game franchises (such as Half-Life, Portal, Left 4 Dead, and Counter-Strike) and leading technologies (such as Steam and Source), announced today a new co-operative game for its free-to-play online action title Team Fortress 2 (TF2).

Available August 15th, 2012, Mann vs. Machine (MvM) lets you and five friends fight a lethal horde of robots on all-new maps, with the opportunity to upgrade abilities and weapons along the way. Band together to survive all of the robot waves in a variety of missions to earn incredible loot and unlock new achievements.

Leading up to its August 15th release, Valve will be making daily updates to its TF2 website, unveiling MvM content and key features. To find out more about MvM, go to http://www.teamfortress.com/mvm.

TF2 is Free to Play for PC & Mac players via Steam. For more information on TF2, please visit http://www.teamfortress.com/.