Die-hard fans of the DC Comics world know that the black suit has some significance in Superman’s history and it makes perfect sense that Zack Snyder would include it in Justice League, since they are bringing Superman back to life.
Zack Snyder loosely adapted parts of the story in Batman V Superman: Dawn of Justice, in that he killed Superman.
But it looks like he will be adapting the “return”part in Justice League which is why using the black suit would be appropriate.
Justice League has wrapped shooting in the U.K. and director Zack Snyder recently shared a behind-the-scenes video showcasing a ton of action from the set of the movie.