LEGO Batman 3: Beyond Gotham has been revealing more future playable characters that will be coming in future DLC packs including the Arrow Pack, the Bizarro World Pack, and the Heroines & Villainesses Pack. For the Arrow Pack, Slade Wilson will be one of these new characters. He is based on the Arrow TV show version.
Roy Harper, aka Arsenal, will also be in the same DLC pack. He is also known by as Red Arrow.
For the Bizarro World Pack, Darkseid will be making an appearance. He will be one of the small number of BigFig characters that is in the game.
Guy Gardner version of the Green Lantern is another character that is in the Bizarro World Pack. I assume he will have the same abilities as Hal Jordan.
The final character revealed for the Bizarro World Pack so far is Greenzarro. He is the alien perversion of Guy Gardner.
It seems that the characters in the Bizarro World DLC Pack comes from the upcoming LEGO DC Comics Super Heroes: Justice League vs Bizarro League original movie. If that is the case, the alter version of Cyborg, Cyzarro, should also be included in the DLC Pack.
For the Heroines & Villainesses DLC Pack, Plastique will be included. At Brick 2014 over in the UK, they have also revealed Terra and Vixen for this pack. This DLC will be a free one that anyone can download sometime in the future. There is still no word at this time when all the DLCs noted in this post will be released.
Update: The lineup for the Heroines & Villainesses DLC Pack includes Raven, Starfire, Plastique, Terra, Vixen, Killer Frost, and Powergirl.