Director Zack Snyder's Batman V Superman: Dawn of Justice has evolved from being the sequel to Snyder's own Superman franchise reboot, Man of Steel, into the 'gateway drug' to (as the film's subtitle suggests) not only the filmmaker's two Justice League movies but the greater DC Extended Universe of comic book film adaptations, since it began development. This new film will continue the story of Henry Cavill's Man of Steel, but at the same time introduce a new (and older) version of the Caped Crusader, Bruce Wayne (Ben Affleck), along with Diana Prince aka. Wonder Woman (Gal Gadot), making her live-action big screen debut.
Justice League characters such as Aquaman (Jason Momoa), The Flash (Ezra Miller), and (at least) the pre-cyborg transformation of version of Victor Stone aka. Cyborg (Ray Fisher) are likewise expected to show up in Batman V Superman in some capacity, as further evidenced by the inclusion of Aquaman in the movie's merchandising campaign to date. More recently though, Snyder took time to re-emphasize that Batman V Superman is, first and foremost, a story about the Bat of Gotham and Son of Krypton.
Snyder has said before that he got the blessing of Dark Knight trilogy director Christopher Nolan before moving ahead with a Man of Steel followup that includes a new Batman, so soon after Nolan's The Dark Knight Rises had opened in theaters. During his interview on the Hall of Justice podcast, Snyder further explained why recasting Bruce Wayne for Batman V Superman (instead of bringing Christian Bale back in the role) was the most logical move to make:
"I think it was weird but I think it also made sense in a lot of ways, because I feel like what Chris [Nolan] did was so complete... it seemed odd to us to try to shoehorn Superman into that world. That seemed more disrespectful to me than anything. So Chris and I talked about it and once we decided we were going to have Batman in the movie, we knew that it was going to have to be a reinvention of that world to make the world make sense with Superman in it. So it just made sense that we would have a new Batman."
By not bringing back Bale's Bruce Wayne for Batman V Superman, Snyder also allowed screenwriters David S. Goyer (Man of Steel), Chris Terrio (Argo), and himself more freedom to create fresh organic connections between their film and upcoming DCEU installments - such as David Ayer's Suicide Squad, which will introduce a new version of the Joker (Jared Leto) whose own history with Affleck's Batman will be integral to the world-building for Batman V Superman and Suicide Squad alike. However, much like the Batman/Joker story thread won't be the focus in either of the aforementioned DC comic book adaptations, Snyder says that Batman V Superman will very much be the 'Dawn of Justice' - and not a backdoor Justice League film.
"I really feel like this movie... I mean as far as the other Justice League characters go, it's very small roles. It's a whisper that they exist. Except for Wonder Woman, we see her pretty well. But the movie is about Batman and Superman. And we really do take time with them, and we really do drill down on the 'why' of them, and what they stand for, and their beliefs, and them as characters. That's pretty much the 'why' of the movie. But again, it does begin the conversation that these guys are out there."
Of course, exactly what Snyder means by referring to the roles of Justice League characters (other than Batman, Superman, and Wonder Woman) as being "very small" in Batman V Superman - well, that's open to interpretation for now. It could mean that filmgoers won't get anything more substantial than a brief glimpse at superheroes like Aquaman and The Flash - simply to establish that they exist in the DCEU - or it could mean that DC's Trinity won't be joined in their battle against villains such as Lex Luthor (Jesse Eisenberg) and his dangerous science experiments until a pivotal moment from the third act. Both of these scenarios have been rumored in the past - though Snyder has also indicated the film will feature the Justice League 'standing together' in some sense (literal or figurative). So really at this point, exactly how the final movie result will unfold is anyone's guess.
Nevertheless, it's encouraging to hear Snyder confirm that Wonder Woman has a relatively substantial role in Batman V Superman - or, to quote him directly, audiences will "see her pretty well" in the film. The character has been highlighted through the trailer marketing for the film to date, but it has been difficult to discern whether she will have much screen time beyond the scenes that've been teased so far. However, both Snyder and Gaot alike have indicated that Diana Prince will have a proper character arc in the film - one that won't distract from the central conflict between Superman and Batman but compliment it, while at the same time further expanding the DCEU mythology and setting the stage for Patty Jenkins' Wonder Woman film due to arrive in 2017.
Indeed, if the rest of the Justice League - however "small" (or not) their roles in Batman V Superman prove to be - are integrated into Snyder's film in a similar fashion, then the movie may yet succeed at both offering a satisfying Batman/Superman story and fulfilling the world-building implied by its Dawn of Justice subtitle. Suffice it to say, every comic book movie fan out is quite interested in learning the answer to that question.
Batman V Superman: Dawn of Justice will hit theaters on March 25th, 2016, followed by Suicide Squad on August 5th, 2016, Wonder Woman on June 23rd, 2017, Justice League on November 17th, 2017, The Flash on March 23rd, 2018, Aquaman on July 27th, 2018, Shazam on April 5th, 2019, Justice League 2 on June 14th, 2019, Cyborg on April 3rd, 2020, and Green Lantern Corps on June 19th, 2020.
Source: Hall of Justice