To say the DCEU is in a bit of a mess right now would be an understatement. The shared universe concept that the MCU popularized, and which Warner Bros. was hoping to replicate, has come to a grinding halt with the negative reception to 2017's Justice League. The upcoming standalone movie for The Flash, with Ezra Miller in the lead role, is expected to provide a reset button of sorts to the DCEU. The director of the film, Andy Muschietti, revealed the basic plot of the movie on Argentinian radio station Metro 95.1, which was subsequently translated and shared on Twitter.
"It is a story of time travel: Flash travels back to try to save his mother. It is a spectacular action movie but it has a big heart."
At first glance, it might not be clear to non-comic book fans how such a straightforward storyline might reorder the whole of the DCEU. The keyword here is 'time travel'. While other sci-fi movies have toyed with the concept of the present being affected by someone tinkering with the past, the upcoming Flash movie will take this concept to the extreme.
The film is inspired by the comic series, The Flashpoint Paradox, which saw Barry Allen aka Flash, travel back in time to save his mother. Returning to the present, Barry finds his actions have set off a chain reaction that resulted in a drastically different reality, where Superman is chained up by the government, Wonder Woman and Aquaman are fighting to take over the Earth, and Bruce Wayne was killed by the mugger in crime alley, making his father the new Batman and his mother the new Joker.
In a past interview, Andy Muschietti has confirmed that he is working on a "different version of Flashpoint than [fans are] expecting," which likely means that instead of showing superheroes turning evil or dying off, the Flash movie will show Barry's attempts to save his mother in the past have reordered the present to have new actors in the role of Batman, and possibly even Superman.
The internal machinations of the 'reset' button Warner Bros. is getting ready to hit with the Flash movie have already been set in motion. During the last 'Crisis' storyline on the CW's Arrowverse, the Flash from the DCEU, played by Ezra Miller, popped in for a quick cameo, confirming that the DCEU is a part of the same multiverse that includes the Arrowverse, as well as a number of other movies and shows, including Tim Burton's Batman films.
All this will pay off when all of reality is reordered due to the actions of the Flash in his solo movie, and the landscape of the DCEU will be a very different place following it, the most prominent example being Michael Keaton's rumored entry into the franchise as a Bruce Wayne of an alternate reality. Ironically, for a movie that is seen as a narrative means of replacing actors in important parts, the role of Barry Allen itself might see a fresh casting, following allegations of assault that Erza Miller is currently facing, casting doubts on his future with the DCEU.