The Flash is finally out and about, and after years of speculation and rumors, all our questions have been finally answered. Being a loose adaptation of the Flashpoint comic book, the film follows Barry Allen (Ezra Miller) as he travels back in time to save his mom and breaks the DC multiverse in the process.
One of the biggest characters in The Flash is, of course, Batman. The film doesn't only pack in the two already confirmed Batmen (Ben Affleck and Michael Keaton), but also includes a cameo from a past actor that certainly answers the upcoming Batman situation the DCU is set to have.
NOTE: SPOILERS FOR THE FLASH WILL FOLLOW.
The Flash features George Clooney return as Bruce Wayne
The Flash heavily deals with the multiverse and introduces it as a concept in the live-action DC films. This is the first of its kind in the cinematic universe and sees Barry jumble everything up once he changes the past and saves his mom. This results in the world not having any metahumans and the Batman being completely different as well.
Michael Keaton dons the Batsuit once again after 30 years and explains DC's multiverse, saying that many times worlds can overlap each other if the past is changed, hence why he doesn't look like Ben Affleck's Batman from the original timeline.
This all comes to a head during the finale of the film, where Barry undoes the damage he did by understanding that he has to let his mother die, but still alters the past a bit so that his father's innocence can be proved in the case of Nora Allen's death. So when he returns, his father is out of jail, and he gets a call from Bruce, who congratulates him for it. However, it's still not his original Bruce (Ben Affleck).
Rather, a car pulls up to the court, and to Barry's surprise, it's George Clooney's Bruce Wayne/Batman that walks out, questioning why he is looking so surprised. George Clooney also reprises the role once more after starring in Batman and Robin, which was released back in 1996, but this still doesn't mean that he will be the Batman going forward.
With James Gunn and Peter Safran set to launch their upcoming new DC Universe, a new Batman film titled The Brave and the Bold was announced to be a part of it, and the post-credits of The Flash very heavily implies that Clooney after all won't be the main Batman going forward, rather his appearance in the film was just set up as a gag.
In the post-credits, Barry can be seen hanging out with a drunken Arthur Curry (Aquaman), who is explaining the multiverse to him. He tells Arthur how he remains the same throughout the multiverse but has instead met so many different Batmen. This can pretty much mean that the casting for a new Batman is still the table and that George Clooney won't be the Caped Crusader going forward. So, it's still not a proper answer, but it still leaves the room open for a new actor to take on the role.
Whatever it may be, we will probably get to know it in a while when the production of The Brave and the Bold ramps up and we get a definitive answer on who the future Batman might be.