I never saw Avatar and will probably never see it. It never interested me. As far as it breaking records...I think some of it has to do with the 3D elements and the additional cost to see it in 3D.
My take is that I don't see younger kids being interested in Avatar. I don't think you can compare it to
Splash Mountain. That ride is themed with cartoon characters and plopped right in the middle of MK! Of course kids will love it.
I think a lot of the disappointment is that so many of us heard rumors of a Dragon themed area or mythical creatures area. I personally woudl have loved to have seen them do something like that as well. Disney has so many animal stories in their vault- they really missed an opportunity.
I am not sure what prompted them to turn to Avatar
Like others have said if it is well themed and the attractions are good then it will be worth it for Disney. I would not make a special trip there to see it but if I was vacationing in Disney then of course I would go. I just wonder how many people would actually make a special trip to see it?