I wouldn't expect much out of them. POI with them like a base, POI designers could add them to any POI if they choose, maybe roaming. But I think that is about all unless they introduce a bandit screamer, which would just work basically the same as the existing screamers. They are very likely to have quests associated with them, of course. And there is supposed to be a faction system, but who knows how that will work.
In the end, other than a different skin and the ability to use weapons, and the expected ducking/dodging/cover mechanics, I wouldn't expect anything really any different from zombies.