Stranger Things’ expanded universe come to if, indeed, season 4 is the last that creators Matt and Ross Duffer plan to make - it would serve as the ultimate climax to the overarching narrative, wrapping everything up in grand style.
On the other hand, though, there’s ample evidence to suggest that this could (and, perhaps, should) still be the case even if Spider-Man: Far From Home was an epilogue for the MCU's first saga.
One of the ways that Stranger Things season 4 could resemble Endgame is if all the characters - including those from past seasons - return to defeat an unstoppable threat or to attend a funeral for someone who's been with them since the beginning. For the Avengers, that included minor players such as Happy Hogan, Okoye, Red Skull, Pepper Potts, Thaddeus Ross, Jasper Sitwell, Peggy Carter, and a whole host of others; for the Netflix series, we could be looking at Terri Ives, Suzie, Dr. Sam Owens, Eight, and Murray Bauman, as well as Chief Jim Hopper and Dr. Martin Brenner (the individuals currently believed to be dead).
Such a cavalcade of characters will also necessitate a number of plot threads previously thought to be tangential, at best, to also return and to be integrated more thoroughly into the main narrative. The best example here is perhaps “Ant-Man films into the main plot of Avengers: Endgame (through the auspices of the Quantum Realm).
And viewers shouldn't be surprised if revisiting all of this material from previous episodes will be done in a strikingly similar manner: Stranger Things’ writers have already demonstrated an affinity for slipping flashbacks into the proceedings, including those that are comprised of brand-new material (such as seeing Joyce Byers and Doctor Strange movies into some of the most critical installments of the MCU.
And, of course, all of this will be done in service of ending the ultimate evil in the universe/multiverse, the Upside Down once-and-for-all. Even if the parallel dimension still manages to creep back in, thanks to the Soviets, in a potential season 5.
