Left 4 Dead 2: The Passing DLC is confirmed by Major Nelson that it will be available this Thursday on Xbox Live.

Also, the following Xbox 360 Game Add-Ons are scheduled to be available:
April 22: Left 4 Dead 2 The Passing, 560 points
April 28: Mega Man 10 Game Add-ons: Endless Attack mode, Special Stage 2 and Special Stage 3, 80 points each.
April 29: Just Cause 2 Game Add-on: Black Market Aerial Pack, 160 points
April 29: BioShock 2 Game Add-on: Rapture Metro, 800 points

Yup, so get ready to find out who doesn’t make it through this chapter. Also, Valve leaked some achievements on their L4D blog.

Warning: The last few achievements contains spoilers.

Torch Bearer
Survive The Passing Campaign.

Port of Scavenge
Play 5 full games of Scavenge on The Port.

Fore!
Knock off the heads of 18 infected with the golf club.

Til It Goes Click
Using the M60, kill 25 infected without letting go of the trigger.

Killing Them Swiftly To This Song
Play the new Midnight Riders song on a jukebox.

Wedding Crasher
As the Charger, grab a Survivor and crash them through 8 chairs at the wedding.

Cache Grab
Open 5 foot lockers.

Kite Like a Man
Kill a tank only with damage from the original Survivors.

Grave Robber
Collect 10 items dropped by a Fallen Survivor.

Mutant Overlord
Play 6 Mutations.

Better not be Bill that passes!