Developer, N Square, a studio co-operated by Nexon and NCsoft, is keeping busy. Its currently developing Mabinogi II : Arena, Project K, and. as of today, officially, Maple Story 2.
The beta will kick off in Korea next year, with information soon to follow for the rest of the world. A Korean site is up currently that may be worth following if you're eager to know more. This site marks the first official recognition of the title's development.