They want Harry Potter. They want Star Wars. They want Avatar.
LOL.
Putting those together is like saying:
"They want ice cream. They want Hamburgers. They want tofu."
Sure, do some fringe people want tofu? Yup. The average person? Nope.
Avatar was a spectacular financial success due to a number of external factors - it was the first "really made for real with 3-D" full-length "live action" (if one can call it that - debatable) big studio film, 3-D was just really hitting "mainstream" cinema (when you could see it in just about every theater that way), and there was little else in the theaters at the time.
But as far as continued public interest, you are sorely, sorely mistaken. I mean, people forget that there wasn't a ton of Star Wars product from about 1986 to 1995, when basically demand had grown so much they had to start releasing figures again (and they never stopped).
Avatar has no legs. Yes, it made a ton of money, and deserves credit for that. But there is no "universe" to speak of, no ancillary product, which is a good indicator of public demand. Even the name "Avatar" is likely to get you blank looks from most people these days (partially Cameron's own fault for using such a generic name, especially one that is already attached to a popular children's franchise). "Oh, that one with the blue people?" Even folks that saw the film would be hard pressed to remember a single character name.
People do not crave Avatar, outside of a small group of rabid fans who think it's the best thing ever invented. The same people that were saying by now every single movie would be in 3-D, and we'd all be craving 3-D. The fad is, again, like it did in the 50's, and again in the 80's, begun to pass. That doesn't mean it will disappear - the studios will not let it, as they want to collect the 3-D tax as long as they can - but the general public has proven they don't much care. It's fun occasionally, but it's not the future. Just like Avatar.
I'd bet you a 7-day park hopper, if Disney starts advertising "Avatarland", more people are going to think it's about that Airbender thing than "that movie about Blue people with the pretty backgrounds".
All that said - I hope the OP is correct. I'd rather Disney spend a billion bucks on just about any other topic than Avatar.