User blog comment:Damac1214/Nuketown Zombies Images Leaked/@comment-5591504-20121111041301/@comment-10363123-20121111041604

It comes with the Hardened or Care Package editions of the game. It would be rare, but a possibility that some shops may have a few Hardened copies left after release. I also doubt that they will release this as individual DLC, as Nuketown 2025 was said to be launch only.