I'm not saying we couldn't see some returning cast, in fact I'm sure a lot of the cast will be regime and insurgency characters from the first game. But the game had a very unexpectedly popular prequel comic that killed off and removed a good number of characters from the universe and the game did the same thing.
As of now in this world we don't have a Lex Luthor, Green Arrow, any green lanterns, Martian Manhunter, black canary(although given the comic she could be back), Shazam, no batman wards expect for Damian, Joker, most of the teen titans, and who knows how many else. If the regular DC universe isn't involved this time then we're going to need to fill some roles.