I'm cool with any batman game made by rocksteady they proved it twice that they can make good batman games, I kinda want to know why Mark Hamil doesn't want to do the voice again, he's done it in so many games and TV shows. Why stop now?
I think it has more to do with him getting old and pseudo-retiring than anything else.
Or, it could be that he figured he was done with the role when they killed off the character.
Pretty sure he has mentioned in interviews that the Joker voice is really physically demanding for him, as well.