Not sure if this is planned, but a simple search of this thread's title hardly came up with any results, and none of them were really my idea. As of now, most bandit camps are more or less the same; there's a bunch of guys standing around campfires in the middle of the wilderness like hobos, and items are strewn all over the place. Needless to say, it's kind of stupid.
What I would really like would be to have small and medium sized bandit gangs move into caves and ruins and use them as their base of operation, sort of like in Skyrim. Particularly large, bold, and well equipped gangs could go so far as to capture occupied castles and towns.
I could also see bandits building forts of their own. It would start as just a palisade and maybe some trenches surrounding a few crude wooden structures, but the fort could slowly expand. It would make sense for the bandits to have a bunker for their leader, a few watchtowers, sleeping quarters, a small dining hall, some cells to hold whoever they take hostage, and maybe a fight pit. Perhqps there could be a small forge and an armory, but as the bandits would get most of the things they need from raiding there probably wouldn't need to be much more than basic infrastructure and a few workshops.
By the time the whole area has been pillaged, the fortress is a respectable hold, and the bandits have enough people, the camp could turn into a town and the gang into a civilization. The civilization would likely start hostile with everyone else, since they'd have a bad history, be warlike, and have very little ethics seeing as the entire populace is just a bunch of renegades and murderers.