But those behind Man of Steel aren't keen to offer easy hints about sequels. "One of the things we dealt with on the Batman films is, Chris dislikes it when you plan something, when you say, 'I'm going to follow this up in the next film,'" said screenwriter David S. Goyer, who co-wrote The Dark Knight series and the screenplay for Man of Steel.
They are thinking too hard on carrying over stuff into next movies.
I mean heck think of the Thor movie. There was the scene of the vault that had weapons in it. One of those weapons is the weapon that supposedly the main guy in avengers 2 is famous for using.
Would it be so hard to have in the background in one of the scenes in Superman be something that could be used in another movie. Not mention it at all, or have it have any significance, just have it be an "easter egg" yet the easter egg ends up being significant later. Or have it be just an easter egg if you change you mind later on story of future movies.
That's what the Marvel movies did best. Most of the cameos or tie in stuff was nothing more than just a quick cameo or easter egg. You could easily watch any of the marvel movies as standalone movies, yet watching them all as one you get a sense of deep collaboration.