DC Cinematic Universe?

The big issue around replacing Affleck goes back to when he stepped down as director of The Batman. It was stated back then that he was looking to get out completely due to all the personal issues he had been going through dealing with his divorce from Jen, plus the flatness that Live by Night encountered.

If he is still unsure about his commitment to playing Bruce, I could see Matt Reeves wanting to make a change also, considering he's signed on for several films.

If they do decide to make a change I would say do it now and get it over with.