Ve3tro writes: " It's been confirmed by Xbox LIVE Editor, Daniel Maher on Twitter that The Passing for Left 4 Dead 2 will release this upcoming Thursday on Xbox Live.
Tweet: "Hey, it's 5pm, which means I can finally tell you that 'The Passing' DLC for Left 4 Dead 2 will hit Marketplace on Thursday. That felt good."
So there you have it, you can grab it on Xbox Live and Steam. At this time no price has been confirmed."