The application's just been filed; it hasn't been assigned to an examiner yet. Standard trademark filing, covering "Drum Hero" for use in all video games.
Now, just because they filed a trademark doesn't mean this is a project in development. They could just be moving to protect the "Hero" franchise, pairing that word and its synonyms with all sorts of instruments just to be on the safe side. So be on the lookout for Sousaphone Hero, Gutbucket Paladin, and Banjo Myrmidon.
Activision ‘Drumming' Up New Hero Game [PlayStation Lifestyle via Hot Blooded Gaming, thanks Troy A.]