Remember they have the staging area for Jurassic World and behind Transformers. Once Horror Nights is over and they remove the soundstage then that leaves plenty of room.
Interesting enough, I had the opportunity to tour Horror Nights during the day with the creative and production team and one of the interesting things they stated was while in stranger things was that the sound stage wasn’t being torn down (only refurbished) and that there is a high likely hood they get to use it for next years event because it is being turned into a space for entertainment/ special events for the Park.