DLC has already been confirmed. This will be great news to the people who bought the Standard Edition as it will contain all 4 original zombie maps, all for the price of 800 MS points!
This info was leaked by Gamestop employees to people asking about the Hardened Edition and its beinifits.
It is unconfirmed when it will be released.
I'm sorry I couldn't get this information earlier, I was very busy. THIS INFO WAS RELEASED ON LAUNCH!