One of the most important things that many fans have discussed when it comes to The Flash: Flashpoint is the fact that the film can offer DC a do-over in the DCEU. Some had previously guessed this would mean a major reboot of the entire franchise, but the ending of Justice League pretty much eliminates the need for that. However, the Flashpoint story arc can still allow DC to make some significant changes by offering current Batman Ben Affleck a clean exit from his role as Batman. If that seems confusing and convoluted, let's dive in and talk this out.
Time travel is a hell of a thing, and the Flashpoint story arc will be rife with the sci-fi trope. At its core, the storyline involves Barry Allen going back in time to save his mother from being murdered at the hands of his arch nemesis, Reverse-Flash. However, his actions have consequences, and he accidentally creates a timeline in which Bruce Wayne died in Crime Alley, and Thomas Wayne (played by Jeffrey Dean Morgan in last year's Batman v Superman: Dawn of Justice) went on to become a grizzled, gun-toting version of Batman. It was recently revealed that DC intends to use Ben Affleck in The Flash: Flashpoint, which means there's already a plan in place to incorporate Batman into the story as a bookend character for the Thomas Wayne version of Batman.
In every version of the Flashpoint story arc, Barry Allen eventually manages to put everything back together. That said, there still needs to be consequences for a Days of Future Past-esque reboot of this magnitude, and one of those effects can be the swapping out of Batman actors. When Barry inevitably manages to reset the timeline, he could easily come back to his original version of Earth-1 and find a new Batman (possibly played by Jake Gyllenhaal, who is the current rumored frontrunner for the part) waiting for him.
Perhaps the most critical element to this entire ordeal is the fact that it lines up with previous comments by Ben Affleck about his tenure as The Dark Knight. Justice League didn't receive the warmest of welcomes at the box office, and the writing seems to be on the wall for him to find a way out of the franchise. Affleck has specifically mentioned wanting a cool exit from the role that will allow him to segue out in a natural fashion, so using The Flash: Flashpoint to provide that segue could be an unprecedented move in the world of comic book movies.
Only time will tell if The Flash: Flashpoint will actually offer up a proper exit for Ben Affleck's Batman. Having said that, the possibility makes perfect sense and seems like a phenomenal story opportunity for the folks at DC to take advantage of when the film finally debuts in theaters.