According to the developer, "On April 3rd, 2013, BattleBlock Theater will be available worldwide on Xbox LIVE. For 1200 Microsoft Points, or approximately $15 USD, you will be able to experience technologically evil cats, friendship, betrayal, co-optional justice, and several other forms of visual and audible stimulation."
Gamers eager to try the game a little early can demo the game at PAX East in The Behemoth's booth (#512).