The Dark Arisen expansion for Dragon's Dogma will be released in Japan on April 25, so it's possible that the DLC might come out in the rest of the world around the same time period.
Dragon's Dogma was a big departure for Capcom from its regular genres, as the Japanese developer created a medieval fantasy RPG that struck close to Western titles like Skyrim or Dragon Age.
The company quickly confirmed that the console-only game was a success and released quite a bit of new content for it, including special modes that emphasized skill and speed.
Currently, the company is working on the full-fledged Dark Arisen expansion for Dragon's Dogma, which has just received a concrete release date of April 25 in Japan, via Siliconera.
Considering the game appeared worldwide on the same day and its DLC was released more or less at the same time across different territories, it stands to reason that Dark Arisen will be launched at the end of April in other regions like North America or Europe.
Expect more details to appear about Dragon's Dogma and its expansion soon enough.