The production crew of [Batman v. Superman: Dawn of Justice](movie:711870) didn't have the best of luck when it came to extras on their set. Early on, one of them leaked a bit of news about Jena Malone's involvement as a new female Robin. Then a couple of months later another extra leaked an even bigger item - giving a description of a scene they believed to be one of the final scenes in the Batman vs. Superman movie.
The leaked info involves Batman breaking into LexCorp in order to get his hands on some of Lex Luthor's coveted Kryptonite stash. It always confused me as to why this would be one of the final scenes of the film - wouldn't Batman be needing to grab the Kryptonite earlier in the movie for his showdown with Superman? There's been a lot of evidence to back up the assumption that Batman vs. Superman ends with a truce between these two guys and a healthy lead-in to [Justice League Part One](movie:401267).
So if this scene does take place at the end, there's a good chance Superman may be asking Batman to steal that Kryptonite on his behalf. The DC comics long ago established a certain bond of trust between these two - with Superman giving Batman a Kryptonite ring (best friends 4eva!) to be used if Superman ever gets manipulated by the forces of evil or simply goes bonkers somehow.
Batman ends up being one of the few people Superman trusts and it's one of the good reasons why a loner like Batman always ends up in the Justice League - someone has to keep an eye on the guy. With part of the Batman vs. Superman storyline looking to involve Superman facing repercussions over all that damage he caused in [Man of Steel](movie:15593), it makes even more sense that he'd be looking to Batman as the guy to keep him in check.
I like this idea of Superman giving Batman, or leading him to, some Kryptonite as an ending to the movie. It does serve as a good lead in to the Justice League and would likely be a nice conclusion to their character's rocky relationship in the movie.
We'll see, it could be that the leaked info about the scene was for something that takes place in the middle of the film, with Batman preparing to get into some fisticuffs with Supes and needing a little Kryptonite backup. Either way, Batman will likely be keeping a chunk of the green stuff close by during his tenure on the Justice League. Superman has a bad history of bad guys getting into his head.