It was announced early on that neither Wonder Woman nor Superman would show up in Suicide Squad. The film has been confirmed to take place after Batman V Superman.
These same streaks of lightning are witnessed in the final Suicide Squad trailer, which showcase Captain Boomerang attempting to rob a bank.
Now it looks like the combo punch of the first Justice League trailer and the latest Suicide Squad trailer have proven this to be true, as pointed out by ComicBookMovie.
And it is believed that he is being thwarted by The Flash in this scene.