They're about to lose the Wild West venue as well, so yes it's three spaces gone next year. They're pretty much forced to bring back Slaughter World, and possibly throw a show in the Animal Actors theater (or Shrek? maybe a 4D horror thing)... maze spaces are going to be tight.
I agree with the revision of Terror Tram, one that brings you to another maze. Otherwise I can't think of a single location. HHN might have to resort to three (or four) mazes, and throw out all the stops. The rest, of course, being entertainment and scare zones.