As was the case with season 3's ending tease of the Russians having a Demogorgon, Stranger Things season 4 volume 2 led to the question of how the Russians acquired the creature, as well as the five Demodogs and some of the shadow particles of the Mind Flayer. The Russian connection to the Upside Down has been completely wiped out by the destruction of the Russian operation in season 3 and Hopper, Murray, and Joyce's destruction of Kamchatka.
With Hopper's rescue and the battle with the many creatures of the Upside Down featuring highly-anticipated romantic moments, the finale of Stranger Things was an incredibly satisfying way to end the season.
The Russian storyline surrounding Hopper was the most difficult to tie into the events in America and the season 4 ending on a strong note. All of this was done in a way that connected the storyline directly to the events of California, making the finale incredibly satisfying and the wait for season 5 even harder. With the fifth and final season of the show being the last one, it is safe to say that its many beloved characters will have bigger, more deadly things to deal with than the Russians of the show's past.
It would make sense, as the creatures and the Upside Down gates would already be in Russia, the same country as the Kamchatka prison, and therefore the complication of transporting them from Hawkins to Russia would be avoided. The world is under invasion by Vecna and the forces of the Upside Down after they were able to open the required amount of gates. The Russians have been involved in the Upside Down and its gates just as much as the Americans in the two most recent seasons of the show.
The Russian storyline of Stranger Things has always been present, with season 1 establishing Eleven's powers as being used by Brenner to spy on Russians and season 3 and 4 expanding the screentime and overall importance of the Russian story. There were many revelations about the nature of Kamchatka, the Russian facility, its connections to the Upside Down, and the story as a whole. The reveal of the Russians having one and the ending of season 3 confirm that the Russians captured a demogorgon and some demodogs and took them to Kamchatka.
The overarching story of the entire show is headed into the final season is one of the reasons why the Russian storyline seems to be over.
The Russian storyline from season 3 of Stranger Things led to questions of how the Russians got so many creatures from the Upside Down and how many Demogorgons they had. The Russians had six Demodogs, and one Demogorgon, for a total of seven that the Russian prison crew needed to overcome. It was hard to see how the Russian storyline would connect to the larger events going on in Hawkins and the main villain, Vecna. The gate the Russians opened beneath Starcourt Mall was most likely used to capture the Demodogs from Stranger Things season 2. It's safe to assume that the Russian storyline will be over going into the fifth season of the show. There was a question about how many of the Upside Down creatures were kept in Kamchatka and how many of the Demogorogons were claimed by the Russians.
Hopper and his crew enter a room in a prison in Kamchatka where they find six dogs and the key to the Russian prison escape. The other five are in suspended animation, which they escape in the finale of Stranger Things, before being burned alive by Murray. Hopper, Joyce, and Murray's antics in Russia were brought to a head in volume 2 of season 4. In the first volume, Jonathan, Will, Mike, and Argyle were sent on a fool's errand to find Eleven.
The Russians had access to at least one Demogorgon, according to the end of the third season of Stranger Things.