“When we started with Man of Steel, we knew that we were going to expand the universe,” DC Films producer Charles Roven told ComicBook.com in an interview. “From the moment that we started with Man of Steel, we knew that once we opened up the Superman… You can’t do Superman without talking about aliens existing in our universe. We knew that we were going to have to really consider what the world building would be beyond the unique film. Then, as soon as Warner Brothers announced that slate, we really got intensive about it.”
“But the thing is, each unique film in the DC pantheon is going to be unique because the directors are different except for Zack directing Man of Steel, Batman v Superman: Dawn of Justice, and the two Justice League movies. Each one of those directors, whether it be David Ayer or Patty Jenkins or James Wan, they are bringing their sensibilities and a different production designer and different costume designer, et cetera. That world building will still be of the same DC Justice League universe, but have its own unique point of view,” Roven said.
Roven also explained that it was important for them to do a Wonder Woman movie before “Justice League”, to introduce her as “part of the trinity of DC Comics”.