One thing to point out to people is that at the time Avatar was still in theaters, there were reports of people
feeling depressed and suicidal and, though I can't find anything of it now I definitely remember it in retrospect, attempting if not outright committing suicide due to being so caught up with Pandora and not wanting to live in a world where it wasn't real. The movie is still the best performing film ever... I personally think I underestimated its sway myself. But you know, as someone pointed out, Fox just never capitalized on the success- no merchandising to speak of, no spinoffs, nothing.
Regarding fandom, there was very much an Avatar fandom. For about a year after the movie came out, even, there were cosplays of it. Just not anymore. The fandom just died because it was just the movie, then nothing else. Fandoms outside of very hardcore cabals of fans can and do die if nothing is being put out officially- I'm seeing it happen with a Japanese franchise very dear to my heart (Sengoku Basara) before my very eyes, and I'm convinced unless Capcom puts out something big (a video game or anime series) of the series soon, it's just going to wither.
With that in mind I'm not really surprised to hear that the banshees are all sold out. While a lot of the film's success had to do with the 3D effects, I still think the world of Pandora itself is captivating to people. There was clearly a lot of thought put into it. And people just love fantasy worlds that feel like they could be real. Now that it, in a way, IS real, I could very easily see it being a draw for people to come to WDW beyond "hey, something new at WDW". Maybe not as big as Potter was or Galaxy's Edge will be, but a draw still. Moreso than probably Toy Story Land or a hypothetical Indiana Jones land.
