While I'll agree with you to a point, if they build something truly impressive - the reputation will get around. I mean Universal got a lot of mileage out of Harry Potter, but if they'd built it on the cheap and shoddy, word would've rapidly got around. It's as successful as it is still today because it is well done.
Another example is Carsland. Do you think there were a ton of people (specifically adults) lining up going "I can't wait for a CARS themed area! YAY!" Carslands massive susccess is due to how good it is, not the IP. (And yes, it is still a better IP than Avatar.)
If Pandora ends up being "the best thing Disney ever did" it will no doubt bring in the people.