One thing to consider is that many attractions take on a life of their own, independent of the success or failure of the original source material. The Matterhorn Bobsleds (inspired by the movie “Third Man in the Mountain”) Mr Toad’s Wild Ride (based on a forgettable animated short that few kids have seen) and Splash Mountain (based on “Song of the South,” which, again, few young people have seen) are some of the most popular, iconic attractions in Disneyland. I haven’t been on the Avatar “Flight of Passage” ride, but several people with no particular interest in the franchise have told me that it was hands down their favorite ride, period. Time will tell if it has staying power, but don’t write off Pandora just yet.
Also, I’m not sure if the contract with Universal on Marvel properties would allow a Wakanda land in WDW, as cool as that would be.