I'd love to see pic related the most, but I have more hope for seeing bad guys than seeing good guys.
Personally, I don't like Abigail that much, but it would make the most sense if we saw her. A fight with Vita and Navy would make a lot of sense, too. Some of the members of the Allen Platoon would also work. You know, they could just build levels around each of the different brigades in the rebel army.
Of course, I'd like to see guys from some of the other factions a lot more, but there's no way we're getting any Amadeus, Ptolemaic, or Invader guys. Especially we're not getting any Red Goblin guys. I have a feeling that they'll stick to Rebels and Mars People. Maybe we'll get some mummies, but I'm not sure.