I'll be honest, there's only three or four scenes from season 3 that really warrant inclusion.
The "Sauna Test," the hospital, Hopper's cabin, and Starcourt.
Two of which we know are coming. And one of those two (Hopper's Cabin) is seen in season 2.
Combining two and three actually makes perfect sense. Stranger Things thrives when it has monsters as the antagonists. The house is going to focus on those scenes.