With everyone in different locations, the season will presumably be about them coming back together, no doubt to fight the Upside Down and/or Russians and whatever they're cooking up with their captured demogorgon.
While we wait for more hints, here are some things that would be really, really great to see:
• Eleven getting her powers back. Last we saw, she had lost them, which is OMINOUS.
• More info about the other kids experimented on. Eleven found Eight/Kali back in Season 2 — but what about the rest of the characters? And what about Eight/Kali herself?! There's so much that could be explored there.
• The return of Dr Brenner. He was Eleven's "papa", and it would be interesting to see both him and Hopper come back from the dead. His storyline has been left open since Season 1. We need answers!
• The return of Billy. Look, he's good eye candy, but it would also be kind of cool if he was somehow in the Upside Down, and came back a changed person. But with a similar arc happening for Hopper in Season 4, the Duffers probably won't go there for Billy.
• Nancy and Jonathan breaking up. I'm very sorry, but Jonathan is the worst and he treats Nancy terribly! Now that he has moved away, it's a good chance for Nancy to have a clean break.
• More screentime for the Scoops Troop. Steve, Robin, Erica and Dustin are the best part of the show and you can't convince me otherwise. I don't even care what they do, because whatever it is, it will be great.
• Will getting some peace. The kid has been through so much. I mean, they all have, but Will really can't catch a break. Let him rest!
• The return of Alexei. This absolutely will not happen. He is dead. But he was so precious and we lost him too soon. This show is full of supernatural shenanigans. It's not too much to wish for, is it?