The reported reason is that Miller's obligations to the third Fantastic Beasts movie took precedence.
Warner Bros. has hit yet another jumble on the road to creating their DC Extended Universe.
Warner Bros. has been particularly slow to get The Flash solo movie to the big screen. The movie was expected to begin shooting in March for a 2020 release, but now, it looks like The Flash won't happen until 2021.
Comic book fans will have to wait a little bit longer to see the Flash race into theaters, and Albus Dumbledore may be partly to blame for the delay. WB and J.K. Rowling have insisted the world needs five installments of the Fantastic Beasts franchise, a Harry Potter spin-off that features Flash star Ezra Miller-who explicitly insisted we call him "Sweet Bitch", you're welcome, Ezra-in a prominent role.
The Flash film, which still does not now have a title, has gone through quite an array of evolutions since the DC Extended Universe's origins.
Since Miller will be preoccupied fighting with wizards, filming for The Flash may not begin until late 2019. That would leave the now untitled film potentially set to hit theaters in 2021, but a formal release date hasn't been set for The Flash. Let us know down in those comments. Talk flared, then faded, about a standalone Flash film would be titled Flashpoint, but after the departure of two directors (Seth Grahame-Smith and Rick Famuyiwa both boarded and exited the project within a span of two years) those plans are up in the air.
After discussing the issues with "The Flash" movie and why it is being delayed, the writers state: "The studio is not now moving forward with Batman and Superman movies featuring Ben Affleck and Henry Cavill, respectively".