Who is this dude?

Wikipedia tells me this is Mayor Kline, but why is he only showing up now? If he wasn't important, he wouldn't have shown up in the trailer. What sort of politic-related plot points could we be in for, other than the opening of Starcourt Mall? Perhaps a new branch of Hawkins National Lab? Is he Dr. Brenner in disguise? Probably not, but we've seen weirder.

What are Nancy and Jonathan doing at the Hawkins Post?

More importantly, who told Nancy that hairstyle was a good idea?

Just kidding. But really, are Nancy and Jonathan planning on releasing some sort of exposé on Hawkins Lab? Are they finally ready to tell the truth about Hawkins and what happened to Will and Barb? Or, maybe they are applying for a job? Something less intense? With the Duffer brothers, you never know.

What will happen to Billy?

When Billy was introduced, I was immediately interested in his character. Sure, he's a major doucheface, but so was Steve when he was introduced. I want to know where Billy's development is heading. Will he become a better person? A worse one? Is he going to end up in some sort of illicit relationship with Karen Wheeler (don't look at me like that, we all saw that scene in episode 9)? We know he's Hawkins's new lifeguard, so maybe that'll teach him some responsibility, but it probably won't. At the very least, he'll get to work on his tan.

Who is Robin?

Obviously, she works with Steve in "Scoops Ahoy", but how much involvement will she have with the main plot? Will she become best friends with Nancy? (Although NO ONE can replace Barb. #JusticeForBarb.) Could she be Steve's new love interest since Nancy is with Jonathan? Or is she just along for the ride? Either way, I'm interested to see what new dynamic she brings to the group.

How will Max and Eleven's friendship develop?

It was no secret that Eleven wasn't a huge fan of Max, in the beginning, worrying that Max would take her place in the party. This promo picture released by Netflix tells us that their feelings of animosity towards one another won't last very long, thankfully. I'm excited to see how they become friends and where their new friendship takes them. Perhaps to the beach, like we see in the trailer?

What the heck is this thing?

I really thought that season two's "Big Bad" would be the Thessalhydra, mentioned in the season one epilogue, but it turned out to be the Mind Flayer. Could the writers have been saving it for season three? Whatever it is, I'm surprised they showed it in the trailer. Maybe this isn't the Big Bad? Could there be something worse that we don't know about? Either way, this has huge implications. Maybe the gate didn't really close at the end of season two, or maybe Will wasn't really cured of his upside-down-affliction.