Just had a random thought for a theory about season 5.

Remember in season 4 when Nancy, Robin, Steve, Eddie...and Theo 😂...were trapped in Upside Down and they go to Nancy's house for guns. But they realize they're in a different time.

And remember in season 2 when Hopper was investigating the pumpkin field at Merrill's farm, there was someone in that field...

What if...Upside Down affects time itself and acts like a Timeline...

A gate, if properly opened, could take a person to a different time.

If they use this in the show and the party thinks they need to go back into time to stop Henry but they need to find the right gate, hence the mystery person in the field. It could have been Hopper himself in that field looking at his past self.

What do you think? It all sounds like Avengers Endgame to me you know?