Recently it has surfaced that Ben Affleck is no longer wanting to play Bruce Wayne as well as Batman. This is coming off of the poor performance (as a film) of Batman vs. Superman: Dawn of Justice, which currently sits at 27% on Rotten Tomatoes. While Affleck leaving would probably not end the DCEU; however, it would not be able to function without The Caped Crusader.
Who could replace Affleck as The Dark Knight?
A recent article by We Got This Covered went into potential replacements, should Affleck depart from the role. Since they broke down each potential in their article, I will keep my own comments to a minimum.
Thomas Jane
Perhaps best known from 2004's The Punisher, Jane is no stranger to the portrayal of a brooding anti-hero. Now, I think Jane could knock Batman out of the park. My only concern with Thomas Jane would be how he plays Bruce Wayne.
Josh Brolin
Brolin is a fantastic actor, but given his involvement with the Marvel Cinematic Universe, donning the cape and cowl would be unlikely.
Armie Hammer
Having decent chemistry with Henry Cavill (who plays Superman in the DCEU) in The Man From U.N.C.L.E., Hammer could draw upon that here going forward.
Julian McMahon
McMahon has not only played Dr. Doom, but he also played the billionaire Victor von Doom. Granted, Victor and Bruce are polar opposites in term of personalities, but that should not be a problem.
Michael Fassbender
As Fassbender's future as Magneto is up in the air and no clear direction where the Assassin's Creed film franchise (the first film sits comfortably at 18% on Rotten Tomatoes). My fear here is that of typecasting. In addition to this point, I feel as though Fassbender would be a great Bruce Wayne....just not a great Batman.
Richard Armitage
Star of The Hobbit films, was actually one of the actors being considered for Batman in BvS at 6 ft 2 and roughly the same age as Affleck, there is the longevity involved and Armitage has the stature; however, he would need to bulk considerably.
Jon Hamm
One of the stars of Mad Men, Hamm could embody both the sophistication of Bruce Wayne and the torment of Batman.
Verdict: Picking strictly from this list, I would pick Thomas Jane. Not going from it though, I would pick Kevin Porter. To see Porter in action, check out the YouTube short Batman vs. Darth Vader.
CONCLUSION
Now each of these actors have their merits, but are all Dark Knight material? Likely not. Now it cannot be stated enough that this article as well as the one I referenced are just speculation and Affleck has yet to comment on if he is indeed leaving the role. As of now, he has only said he will not direct a solo Batman film. If Affleck decides to leave the role, his last portrayal of Batman will be Justice League Part 2 in 2019.