The film was originally slated for a 2018 release date. But with too much meddling on account of WB Studios and switching of directors and core cast members, the date was pushed back to 2020. In the comics, the Flashpoint storyline involved Barry running back in time to save his mother. As a result, the alternate timeline turned Metropolis into a wasteland, Kal-El never became Superman, Bruce Wayne was dead and the Atlantean-Amazonian war threatened to engulf the entire planet in flames.
The movie is adapting elements of comic book storyline and Ezra Miller is pretty psyched about all the Thomas Wayne stuff. Here is what he said:
“Oh, hell yeah. I think he’s amazing, and I think he would fall right into what is becoming a very, very serious ensemble of actors. I’m so excited about Kiersey Clemons. I’m so excited about Billy Crudup. I just couldn’t be more stoked about the names involved so far. I think that the emotional arc of the Thomas Wayne stuff in Flashpoint is one of the illest parts. And to see that different manifestation of Batman and his whole different style.”
“And I love the reality that you have this universe that is so inverted from the one that we know. And this one factor remains the same, but in this flipped way. Batman is steady, but it’s going to be the result of a different side of the same tragedy with Thomas Wayne instead of Bruce, and that’s dope.”