All right, so Battleblock Theater doesn't have a release date yet. But The Behemoth offered a superb visual justification for why it takes as long as it does with each game: footage of an early version of Castle Crashers, back when it was a GameCube game and purely a side-scroller. "We decided it was cool but NOT COOL ENOUGH," Project Manager Emil Ayoubkhan said on the development blog.
"So anyway, this is why we took it back to the drawing board. We needed to tweak stuff and add awesomeness on top of it. This is essentially what's happening with BBT right now," Ayoubkhan explained. "Some of the largest steps forward have occured recently and we're so glad we didn't just settle on something that wasn't quite ready yet (and at the same time ready to explode from the excitement of handing it over)."
This example suggests that Battleblock Theater could go through some dramatic changes before we finally get to play it. It also suggests that, if development progresses like Castle Crashers did, we'll get to play it.