The DLC planned for Prince of Persia is to be of "significant value," as noted by Ubisoft producer Ben Mattes in an interview with Gamercyde (at the 19:12 mark). Mattes doesn't believe the PoP DLC will be character skins or weapons, but will be "a new story, a new experience, maybe a prequel, maybe a sequel." This is all said under the caveat of "if" the team decides to do DLC.
If the team does decide to do some DLC, it will arrive sometime next year, but the whole thing is "still in discussion." We'll worry about DLC later -- right now we're itching for the Prince and Elika to make their way onto our consoles in two weeks.