The park has a lot to do with it, though. It's a perfect fit, because of the other offerings, or lack there of, in that half day park. The ride system, the experience and the press it will generate. I think you're underestimating the wow factor and how popular the film was.
I will say I'd rather have that Mysterious Island/Beastly Kingdom hybrid that was planned at one time, with a clone of Mystic Manor (my Pipedream, not what was planned), but I'm not sure they would be as big of draws as I think Avatar will be.
If anything, I think this could encourage more growth at AK.