It’s been reported that David Dastmalchian was recently cast, apparently to play Polka-Dot Man. Beyond that, THR says that the rest of the new team will be made up of the characters of Ratcatcher, Peacemaker, and King Shark.
Article source: https://www.cinemablend.com/news/2471037/who-suicide-squad-2s-new-characters-will-reportedly-be