Zack Snyder, the director behind 300 and Watchmen, will be taking on Man of Steel in about six months--this much we know. Most fans have speculated that, with a rumored release date of 2015, Warner Brothers's Justice League movie will have some connection to Man of Steel, although that has been speculation up until now.
Except that Snyder is teasing a connection between his iteration of Superman and the rumored JLA movie.
“I don’t know how Justice League is going to be handled. Honestly, I don’t,” Snyder told the New York Post. “But Man of Steel exists, and Superman is in it. I don’t know how you’d move forward without acknowledging that.”
Playing a little bit of semantics here, one could point out that it sounds as though Snyder is acknowledging that Justice League is in development--something Warner hasn't formally done up to this point--but other than that, this isn't really much in the way of news.
Asked directly whether Man of Steel might kick off a DC cinematic universe, though, Snyder gives the kind of non-answer that's clearly hiding something big.
“Um, how can I answer that?” the Post quotes him as saying. “I can’t really say anything to that, because that’s a big spoiler. I will say, yeah, they trust me to keep them on course.”
That the question of a DC Cinematic Universe would be "a big spoiler" will point, in most fans's minds, to a big yes, and of course now starts the speculation as to what might be the big spoiler in question. A Wonder Woman cameo has been teased already, and of course there's the always-popular idea of Batman showing up in the film. Maybe even something as simple as Superman being offered an opportunity to chair the Justice League, with no concrete clue as to what that means until later.
In any case, look for a formal announcement of Warner/DC's next move around the time the Superman film bows, if it hasn't happened by then. If there's a cameo or tease of an upcoming film in the movie, that'll blow the opportunity for Warner to announce it the way they want.
While it's not Snyder who mentions it, the article also suggests that Warner is likely to discard Green Lantern, and officially launch any DC Universe with Man of Steel, giving the company a clean starting point with no connection to the existing Batman or Green Lantern films. For Snyder's part, he told the reporter it's a question of focusing on the film first and worrying about the rest as it happens.
“We approach the film as a single endeavor,” the director said. “There are a lot of gears that have to turn in the world of commerce and the world of the mythology we create to facilitate more adventures for this character. We’ll see what happens.”