Zomg Zomg Zomg.....I just found a post online about the new campaigns.
“is to get at least one more update out before L4D2 comes out so we’ll be announcing more on that probably in a couple of weeks.”
Here's the link:
Destructoid - More Left 4 Dead Xbox 360 content is coming
I found this on another site: Following up on earlier reports that Valve won't leave Left 4 Dead to die an early death, the company stated today that there should be an L4D DLC announcement before the end of summer. A company spokesperson also told CVG that about eight or nine months from now, when L4D2 has released and people see the continued support for L4D, they may finally understand the method to the madness.