"The Official PlayStation Magazine U.K. may have revealed a few new features about Batman: Arkham City today, including a feature that had been talked about before.
According to their story, the game will be five times the size of the original game, and will give Batman a Grappling Boost to launch him long distances quickly. When asked about vehicles in the game, a Warner Bros. PR representative said that it's "something we'll cover at a later date."
As for multiplayer, it was described that Catwoman could use her whip the way Batman uses his grappling hook. When asked if she'd be controllable in co-op, game director Sefton Hill said he was "not allowed to comment on that."
The game looks to be still on (I assume you are talking about the game and not the TV show). This celebrity list was just released a couple of days ago, and the game is still listed on the manufacturer's website as 'coming soon'.