My understanding is that he's not under contract, but there's still discussion about him continuing the role. Not sure he's quite as massive as most modern bodybuilders, but regardless of that I'd imagine he probably just enjoys the gym rat life.
I won't speak to how good he'd be as Batman, but Pattinson is actually a rather good actor. Check out 'The Lost City of Z' and 'Good Time' to see what he's capable of. He'll never lose the stink of Twilight on him, but even the greatest actor in the world wouldn't have been able to perform well in those piles of shit.
I think if Pattison Muscled up for the role, he might be descent. His current body conformation is what throws it way off. He has more of a riddler body than a Batman body. He can actually act, as was noted a couple of posts up. The Twilight series will always follow him just as much as the actors in the Harry Potter films are forever tied to those roles.