The first clash between Batman and Superman will have a winner, and bets are already placed. However, it may not end as we expected.
From the current stream of plot rumors and dissections of the trailer, it is known that at first, Batman hates Superman. They fight, but the emergence of a greater threat will force them to unite to save Earth. Then, other heroes like Wonder Woman emerge and they form the Justice League.
That would be too predictable for someone like director Zach Snyder. There may be clues for the future in his interview with Empire magazine (h/t Screen Rant):
"We want to assume that Batman has reached this point in his life and career as a superhero, and Superman represents a sort of philosophical change," Snyder said. "He is a paradigm shift for Batman: 'I've been fighting criminals all my life, trying to find justice, and now I am confronted with a concept that is transcendent to me.' In the face of Superman, a man robbing a bank doesn't matter.... He's having a crisis of conscience. 'Am I really just a vigilante who stalks the alleys of Gotham?' It is rich stuff that he deals with. Ben does an amazing job."
This personal dilemma leads him to oppose Superman and eventually the 'metahumans' and Batman, with the Kryptonite tease, would probably win. While there is a possibility that they will settle their differences in the end, it will not be as predictable.
What Culture predicts that Batman will be in the events that lead to the formation of the Justice League ("dawn of justice") but he will NOT be joining the team. It would be consistent with the "tired and weary" projection of the Ben Affleck Batman, and the last thing he would want is to join a team of superpowered metahumans.
"(The) Dark Knight would inevitably end up joining them, teasing the prospect of the team heading into battle without him initially opens the door to some very exciting storytelling possibilities."
Despite the idea that there are "good guys" and "bad guys" Batman will still harbor some distrust and maintain the separation from humans and metahumans.
If, and how this narrative will unfold is a good reason to keep fans guessing and avoid being predictable. Marvel has already had some shockers (Mandarin) and the idea that superheroes don't get along (Civil War) but Snyder and the Dark Knight will take it to an entirely new level.