
Its not just some troll rumour. @ E3, Valve Officially Announced a November 17 2009 Release for L4D2.
http://store.steampowered.com/news/2552/
Coming exclusively to Xbox 360 and PC, L4D2 promises to set a new benchmark for co-operative action games and become one of 2009's marquee titles.
"A large part of how Left 4 Dead became 2008's top-selling new IP on Xbox 360 and the PC was the custom-tailored gameplay made possible by the AI Director," said Gabe Newell, president and co-founder of Valve. "With the knowledge gained from creating the original, new technology, and a passionate team, L4D2 will set a new benchmark for cooperative action games."
Set for release on November 17, the title adds melee combat to enable deeper co-operative gameplay, with items such as a chainsaw, frying pan, axe, baseball bat, and more.
Introducing the AI Director 2.0, L4D's dynamic gameplay is taken to the next level by giving the Director the ability to procedurally change weather effects, world objects, and pathways in addition to tailoring the enemy population, effects, and sounds to match the players' performance. The result is a unique game session custom fitted to provide a satisfying and uniquely challenging experience each time the game is played.
Featuring new Survivors, boss zombies, weapons, and items, Left 4 Dead 2 offers a much larger game than the original with more co-operative campaigns, more Versus campaigns, and maps for Survival mode available at launch.
Its a slight kick in the gee. They set the Precedent with TF2 that they would continue to milk the game like a cow. Especially considering how agressively they marketed L4D.
Still, reading the Press Release, its obvious that it precedents almost a complete game engine change (not Source, just the Zombie stuff) by Overhauling the AI Director, and changing the Boss Zombies. In addition, this Path generation, is something that seems like nothing but goodness to me: imagine playing No Mercy, and never being sure of which way you would be able to take each time, as the alleyways, apartments, sewers and streets would all change dynamically from play to play.
Clearly they have some big ideas for L4D and yeah, if its as big as it initially sounds, I can see how they justify a complete new Title.