I hate to say it, but this wouldn't really surprise me. While the movie itself was visually stunning and the story somewhat entertaining, it has several issues that I think make it difficult to re-create in a real-world/theme park setting. The biggest issue I see with it is the antagonist in the movie is us, the human race and our greed to possess the treasure of Pandora, unobtanium. With the way the movie ended, WE ARE THE BAD GUYS! Why would the Na'vi welcome us back?
Aside from that, another issue I see is in crafting a story line that will magically transport us from planet Earth to Pandora (and back). The movie set it up quickly and easily by beginning at the end of the 5+ year trek from earth with the characters waking up from cryosleep. This problem isn't as big, because it could be handled in the same manner as it's done on Mission:Space at Epcot. On this ride, the narration simply tells you that it's time to go to sleep, then just moments later wakes you up. But, even with the supposed 5 year journey simulated, what would be our reason for visiting Pandora. Since we're at DAK, I'm guessing it has to be something tied to the conservation theme, along the lines of helping the Na'vi for some reason.
Perhaps the best solution might be to take us back in time in the story when Grace and the others are still running the school referenced in the movie. We could be part of the education staff, teaching and studying the Na'vi and Pandora, before everything fell apart. Since it's a part of the story that was only lightly brushed over in the movie, it could be re-told in a way that would put both us and the Na'vi on more friendly terms. Another option would be to go back even further in the timeline and make us some of the first visitors sent on a mission to explore the planet and establish peaceful relations with them.