Presumably Negan has another base, since we know the actor who will play him did not appear in the episode.
Though he lost a lot of men, armory and pantry.
Then again, if they had another army, the Alicia Witt character wouldn't bother negotiating with Rick. They wouldn't take hostages, they'd just go to the other base after killing them.
In the Talking Dead preview, one of the bad guys is an old guy whom Carol must have cut and says something about needing to negotiate for Rick's prisoner to patch him up. So they can't have much resources left. Besides the wounded old guy, there was an old woman and Witt, who's not so young either.
Yet they all have attitudes, like they're superior and have an advantage.