Hero Complex has following from Snyder:
In his tchotchke-filled office on the Warner Bros. lot, Snyder confirmed that the seed for “Justice League” — a DC Comics equivalent of Marvel’s “The Avengers” that features a superhero A-list including Aquaman, Batman and Wonder Woman — has indeed been planted within “Man of Steel.”
“Do the DC characters exist in the universe I created? The answer is yes,” Snyder said. “In my mind, we have this fantastic character of Superman. It’s not madness that there would be others.”
“Now, that being said, does a ‘Justice League’ movie exist now? No,” he continued. “Whether or not I ever get to make that movie, I don’t know.”So the seed's in the film? That's excellent news, and something to keep an eye out for (aside from the already known Easter Egg we mentioned before).