Good eye! It does look like Hopper's cabin in the background of the video with the porch light on, which is likely a reference to how the next season will focus on his rescue. But it could also be a clue to where he is. We've talked about Hopper possibly being the American in Russia, but what if Hopper is actually trapped somewhere a lot more familiar, like the Upside Down? That would give a new meaning to the line "We're not in Hawkins anymore," which could actually be more of a reference to The Wizard of Oz. Just like Dorothy, Hopper could be trapped in an alternate world that mirrors his own but is much darker and more dangerous. Welcome to Hawkins, indeed.
This theory definitely holds some weight when you look back at the video, since it's basically Hawkins turning into the version of the town that we often see when Will or Eleven flash into the Upside Down. It also brings us back to that voicemail from Murray Bauman, where he asks that Joyce call him back because he has some news that's "not good or bad, but it's something." Hopper being trapped in the Upside Down isn't bad because, hey, at least they know where he is, but it's not good because . . . well, he's in the Upside Down. Sure, he's been there before, and he has a pretty good handle of the layout, but it's bound to drain him before too long.
The idea that Hopper is trapped in the Upside Down also calls back to that heartbreaking final message he left Eleven. He asked that she please leave the door open three inches — what if that's all he'll end up needing to find his way back home? If season four does end up taking this route for their new location, we hope the gang figures out how to rescue Hopper ASAP because something tells us they're in a race against time.