One of the major laments of "Left 4 Dead 2" (mostly before its release) that was that besides a very far-away cameo, the survivors from the original game were absent from the sequel. Come the spring, that problem will be taken care of as Valve has announced that the first DLC for the critically acclaimed sequel to the critically acclaimed first person Zombie shootout will include the original iconic survivors and some other goodies as well:
In addition to the new co-operative campaign and associated narrative, "The Passing" will include new arenas for Survival, Versus and Scavenge mode and introduce a new co-operative challenge mode of play. The Passing will also include a new "uncommon common" zombie class, melee weapon, and firearm.
The dialog between characters is one of the hidden charms of "Left 4 Dead", so beyond the joy of playing with familiar faces I'm excited to see what kind of banter goes on. The "Passing" is tentatively set to be released in the Spring of 2010.
Valve Press Release