She also mentions something about a baby during the credits.
HUGE Easter Egg (Saw on Reddit)
@Edwardryu: Just in case this was a serious post, Joker's baby (assuming it was him that impregnated Harley) would be like, three years old by the next game, barring comic book mischief. Not a likely super villain.
I think we will get one more game with the current Batman and then it will jump to Batman Beyond where Joker's son can take over his role.
This edit will also create new pages on Giant Bomb for:Beware, you are proposing to add brand new pages to the wiki along with your edits. Make sure this is what you intended. This will likely increase the time it takes for your changes to go live.