In an interview with Film Comment, Nolan explained the ending of his “Dark Knight” series.
“For me, The Dark Knight Rises is specifically and definitely the end of the Batman story as I wanted to tell it, and the open-ended nature of the film is simply a very important thematic idea that we wanted to get into the movie, which is that Batman is a symbol,” explains the Dark Knight trilogy director.
“He can be anybody, and that was very important to us. Not every Batman fan will necessarily agree with that interpretation of the philosophy of the character, but for me it all comes back to the scene between Bruce Wayne and Alfred in the private jet in "Batman Begins," where the only way that I could find to make a credible characterization of a guy transforming himself into Batman is if it was as a necessary symbol, and he saw himself as a catalyst for change and therefore it was a temporary process, maybe a five-year plan that would be enforced for symbolically encouraging the good of Gotham to take back their city. To me, for that mission to succeed, it has to end, so this is the ending for me, and as I say, the open-ended elements are all to do with the thematic idea that Batman was not important as a man, he’s more than that. He’s a symbol, and the symbol lives on.”
Cinema Blend feels that this statement enforces the possibility of Gordon-Levitt donning the mask and cape to team up with his superhero cohorts in “Justice League.” SPOILER! If Batman isn’t necessarily Bruce Wayne, Gordon-Levitt’s character John Blake, aka Robin, could logically be the successor of Gotham’s golden boy.
As of now, however, there is no reason to believe Gordon-Levitt will ever wear the bat suit on the big screen. Hollywood.com reports that when contacted, the “Looper” actor’s representatives “refuted the rumor entirely.”
This doesn’t mean that audiences won’t get Gordon-Levitt in the DC Comics crossover, but the odds are against it happening.
Nolan’s Batman series takes place in a universe helmed in reality -- for the most part. The “Justice League” movie will tie into Zack Snyder’s “Man of Steel,” among other DC movies, which will take place in a universe with aliens, superpowers and other fantasy and sci-fi elements.
The open ending of “The Dark Knight Rises” can be used as a tie-in to another film, but that isn’t what Nolan intended. It’s a symbolic gesture that acts as a reinforcement of the concept that Batman is less about being a physical being, and more an idea that people can take back Gotham city from the criminals that run it.
"Justice League" is scheduled for a Summer 2015 release.