Well, we know at least one spin-off is already happening...
Yeah and from what I gather it's vastly different from the show thus far. One presumes that the idea here is to continue with the original concept for the show which was much more bent towards anthologies; or rather anthologies of serialised stories, so 'Stranger Things' won't just be "that 80's show set in Indiana", but more of a brand umbrella more akin to say 'The Twilight Zone', or I guess Cloverfield on the cinematic side (sub-optimal example, I know!)
Which is why I specified "sequel milking", as in just straight up sequels, spin-offs & prequels based on these specific characters. All of that would be hard to do if they end the show in a very definite way. For example, they can't do a "Steve & Robin go to university and it's basically 'Animal House', but with more lesbians" if half the world got chomped by a trans-dimensional conversion and an irrevocable biosphere contamination. Or a "Dustin & Suzie get recruited by the CIA" espionage comedy if most of the world governments are either gone or unrecognisably rearranged.
You raise a good point there. I hadn't sussed on the different genres for each season, at least to the degree of seeing a correlation that each season highlighted a classic 80s genre. With that in mind, I could see that happening but it still feels like a pretty stark contrast with the previous seasons and I'm not sure if the Duffer Brothers would make such a large jump.
Why not? It the final season, it's not like they have to worry about writing themselves into a corner.
Also just think of the material they have to pull from; 'Blade-Runner', 'Mad Max 2: The Road Warrior', 'Mad Max: Beyond Thunderdome', 'Escape From New York', 'The Running Man', 'Cyborg', 'The Terminator', and those are just the memorable ones; there's a whole slew of more obscure stuff like 'The Quiet Earth' & 'Testament', along with many many other much more shlocky, cheesey weirdness they can channel.
Hell they could even take some inspiration from the anime side; 'Nausicaä of the Valley of the Wind', 'Akira', and 'Fist of the North Star' certainly leap to mind, and are of that period!
'Nausicaä' feels especially like a good source of inspiration given it's setting is literally about the last survivors of humanity being pushed to the brink by an aggressive, encroaching eco-system that's actively trying to kill them.