I think we all agree on this but Netflix is going to milk this show until the cows come home. It's one of their most successful original shows so we can expect more for sure which means they're going to ruin it exactly as you have laid out. The story will be taken too far. The situations and personal relationships will become absurd. The writers won't care despite the fact that they will be bereft of ideas. It's all about the money money money (and let's face it, Netflix is gonna be strapped for cash at some point in the future because they are already over-extended).
Personally I'm tired of the "upside down" story and would prefer they do something else. I'd be cool with vampires or werewolves or something like that. But watching Will whine about being possessed by the shadow monster has gotten boring.
*I will admit that Winona Ryder does a good job playing the harried single mom. It's kind of sad that physically she's aged like milk left out on the kitchen counter, but at least she's still getting work, so good for her.
Poor Wynona! But hey, her acting chops are on the money in this show. You are probably right about the story being taken so far. This is exactly what happened with Under The Dome. I read the book, and I know when it ended. The series changed the real ending and stretched an entirely new, utterly ridiculous new extended storyline which was absurd beyond belief. And they had the NERVE to tack on a mystery ending like there could be another season (as if)? They did it with 12 Monkeys and started to do it with Continuum. Once Upon A Time is still running on borrowed time as well.
This particular show will not benefit from being stretched out. Will Nancy finally be able to say she slept with ALL the males in town over the age of 18 and under the age of 30? Will Dustin stick his fingers in a light socket and suddenly be able to speak Klingon? Will Jonathan and Nancy have a threesome with Steve?
Or, they can do a time travel thing...