If marketing/publicity people know about the stuff that goes on, I would absolutely thing they would encourage it or try to play to it. Maybe in a balanced way, so that people's expectations don't go TOO crazy - but maybe that's left to the showrunners, who want people to actually react to their show for what it is. It is interesting, and for a while honestly I couldn't think of a fandom for a Netflix show. But then I suppose Stranger Things really took off - and there are probably a bunch of other ones I haven't thought of because Netflix makes too many things to keep track of. In a way I really miss the old way of watching TV shows, where things were quite episodic, and you got that week of waiting where you could anticipate and discuss with people what might happen. But things change I guess, and the 'all at once' system has it's own good points. As for films, I'd say it gets a little murky given how many films are adaptations of other things nowadays - so a lot of people already know roughly what the characters and story and plot might be, and are already fannish about that, and bring those expectations to the new films. I certainly saw Avengers fic for at least a year before any of those characters met, and I really couldn't tell if it was comic stuff or anticipatory-for-the-film stuff, or suppose to be a mix of both. Fandom is changing I guess. Or maybe some of it was always like this, and I'm only remembering the 'golden age' parts :)