People started freaking out when they heard about Warner Bros. calling for more scenes to be shot. The rumor was that they wanted to make the movie funnier, since BvS: DoJ was getting crucified for not being funny enough. According to the director, David Ayers, this is not the case at all.
If I had to guess, they probably called for some extra shots once BvS: DoJ did well enough at the box office to make the Justice League movie a certainty. I wonder if they were waiting for that before showing how much Batman was involved. Maybe someday we will find out.
Also, from the way it seems in the preview, the Joker is not part of the team. Does he maybe free them from the government control and the team becomes splintered. Deadshot and a few others wanting to do their “good deed” and maybe get released, while someone like Harley Quinn just wants to be with Joker. Is that why Batman is there trying to stop them?
Yeah, I am excited for this movie.