So a sequel for Arkham Asylum has been announced and it's coming out next year. While we don't know a whole lot about it, there is a cool secret in Arkham Asylum that hints at Arkham City. I finished this game 5 times and searched every area multiple times, and I still never saw this secret. If you want to check it out follow the link.
http://gameinformer.com/b/features/a...cret-room.aspx
I'm going to go for a 6th playthrough now.