Wrapping up a big series like this is very hard, as Lost famously showed. With one episode to go, I think the Duffer Brothers have done about as well as anyone could expect with wrapping things up well. (I do like that we finally got an explanation for how they all ended up at the radio station, via Max.) We'll see if they stick the landing.
I think everyone but the core kids is expendable -- they're repeatedly putting Karen Wheeler in danger of dying -- but I'm not convinced they'll kill any of the original crew.
Killing Will, Robin or Vickie would play into the very bad "kill your gays" trope, although Vickie otherwise has "killed by a monster" written all over her.
I think Steve and Dustin's "if you die, I die" pact certainly means we're going to come close, at least, to losing one or both of them, although given what Dustin has gone through after Eddie's death, that would be pretty cruel to do to him a second time. Likewise, Max and Lucas are probably safe, for the same reason, with Max probably getting her mobility back at a dramatically appropriate moment.
The science teacher -- whom they should have brought in on the secret at least a season or two ago -- is almost certainly dead meat.
Murray, who hasn't had much to do this season other than to deliver plot coupons, is probably going to be given one great final scene and exit the series in bloody fashion.
Kali almost certainly won't be making it out of this alive. I get the idea that we're supposed to be rooting against her, but she's not wrong with anything she's said so far.
Hopper and Eleven also seem to be in danger of not making it back to Hawkins, although Eleven being trapped in the Abyss once the Upside Down is destroyed also feels like an appropriate ending.
