Batman Arkham City Possible Sequel

Alright heres my what I've come up with from playing Arkham City and the hints that I've found in the game for a sequel.
For those that have believed that Harley is pregnant with the Jokers kid sadly this has been proven false with the DLC Harley's revenge as she retook the test a dozen times and each was negative.
However if you listen to what the inmates are saying throughout the game after you've beaten it you can put together a couple of clues that led you to a couple of conclusions, one being that the Joker will return.
A number of the inmates discuss Jokers death, and a number of them say that the Joker has died a number of times, so many in fact that they've lost count. Another is the inclusion of the Lazarus Pits in the game and there's no mention of what happened to his body after he died.
Another more obvious route would be Thomas Elliot as Hush looking like Bruce, meaning they could be going with the whole Hush story line for the next game. Or even the event that Azrael was talking about when you finally found him.
Not to mention the Man-Bat Easter Egg in the game that could come up in the sequel.