The new campaign is called "The Passing" and takes place right after the events of "Dead Center". Sadly you will only be able to play the L4D2-cast feat. Rochelle and Co.

“The Passing will become the most important campaign in the Left 4 Dead story, as all the Survivors are being called together in one campaign,” said Doug Lombardi, VP of marketing at Valve. “It will also be a huge offering of new gameplay content, with something new for every game mode plus a new uncommon common and weaponry.”

So as he mentioned there will be new stuff also, the most important is for sure the new special infected. Maybe on of the old survivors will turn into an Infected and haunt us for the rest of his (undead) life? Plus there are new maps coming out, well of course, taken from "The Passing" and new weaponry. So my idea of implementing a lawnmover finally came true! And I'm really curious about the new co-op mode...

What do you think, what could the new infected look like and what should be its special ability?