OK, here's the thing: I don't care about the movie. I don't need to have seen Pirates of the Caribbean to appreciate it as a well-themed, interesting ride - which is good because the ride existed before the movie.
Really what I'm trying to say though, I feel there are very few rides at WDW (can't think of any in fact) that have value only if you have seen the movie or are familiar with the background, or lose anything if you're not up on the backstory.
I trust that Disney Imagineering will succeed in creating Avatarland as a beautiful, immersive experience that does not require you to know any backstory, nor leave you feeling like you're missing something if you haven't seen the movie that was the basis of the experience. I don't anticipate that it will be something that people will give only 3 stars if they haven't seen the movie, but 5 stars if they did. Given that, is there any reason to lose excitement just because the movies may not line up temporally? I don't think so. So yes, I am excited about Avatarland.