In the beginning of the trailer, we can see “Eliminate attackers:16 remaining” , however there are only 24 players in this mode. Assuming teams need to be balanced,one team will not have 16 players, there would need to be three teams.
So, is that third team the new Promethean soldiers? We can only see two teams of spartans, so this would be the only logical conclusion as the prometheans are the only thing that do not share colors with a spartan team.