Included in the pack are competitive maps Banzai, Sub Pens, and Corrosion...but what intrigues us most is Shi No Numa -- "Zombie Swamp". Among the new features of Shi No Numa: perk machines, the experimental Wunderwaffe DG-2, and -- get this -- flaming Hell Hounds.
We can pretty much bet that for consoles, the new DLC will cost $10 again. It remains to be seen whether or not PC users will get it for free again.
UPDATE: According to Treyarch's community manager, this map pack will be available in June.