Killer Croc - After growing much bigger than he was in Arkham Asylum and Arkham City, Croc is sure to be voiced by someone that can perform a much deeper tone of voice than Steve Blum's and the man that is sure to replace him on voicing the villain is the Dark Knight's Keith Szarabajka After voicing Ronan the Accuser from Avengers Earth's Mightest Heroes and Living Laser from Ultimate Spider-Man Szarabajka should have the perfect voice to fit Killer Croc in Batman Arkham Knight and if he does not end up being the voice of the character then it will most likely be Fred Tatasciore
Mr. Freeze - With Maurice LaMarche not involved in the game since his name along with two others were not accounted for in the end credits, he is sure to be replaced by someone who is and the one voice actor in the credits that should be able to provide a voice similar to LaMarche's is Dave Fouquette (voice of Ghost Rider from the 2007 movie adaption videogame)
Mad Hatter - With Peter MacNicole absent from the game along with Maurice LaMarche and Dee Bradley Baker, Michael Cornacchia is expected to replace him as the voice of the Mad Hatter in Batman Arkham Knight
and finally
Ra's al Ghul - Since it has been revealed that Dee Bradley Baker is not in the game, he will most likely be replaced by Steve Blum since his voice can sound similar to his at times Until the release of the Season of Infamy Side Mission expansion DLC keep your eyes open for anymore updates that Rocksteady gives us