Dimitri, played by Tom Wlaschiha, is an important part of Stranger Things season 4. He befriends Hopper, sort of, and then, after their plot to sneak Hopper out of the prison is discovered, Dimitri and Hopper lean on each other to survive the Demogorgon pit.
Like all of the other characters on this list, Wlaschiha is missing from the main cast photo for season 5, which isn't a good sign that we'll see him in a big role. At the end of season 4, Dimitri didn't take the trip to Hawkins with Hopper, Murray, and Joyce. We don't know what exactly happened to the Russian, but he's been through a lot. Coming to America to stop an interdimensional monster like Vecna seems like a bad time.
Again, there are so many characters who will play integral roles in the final season. It would be great to see Dimitri again, but unless we're going back to Russia in season 4, which shouldn't happen, he probably won't be in the new season.
So, that's the list of characters we aren't expecting to see in Stranger Things season 5. It's definitely going to be weird without a few of them, namely Eddie Munson, Argyle, and Dr. Brenner. Argyle is the one I'm most surprised to see left out, but it probably makes sense when you think about how many characters there will be in the final season.
Stay tuned for more news about Stranger Things season 5!