Its a bust not in terms of interest but in having that cult following to it. Why WWoHP and all the rest of Disney is so sucessful is because of its cult following? Why do you hear people yelling and screaming at Disney to make Star Wars Land (huge cult following) or Pixar land again such as carsland (huge cult following). We live in a time and era unlike the earlier times where theme parks could create new 100% original themed rides and still be wildly popular and make people run and rush to the parks. Yes Avatar was great in movie sales, yes it was one of the most watched films but how many people do you hear raving at it. How many people are like Avatar is the best movie ever and have viewing parties just to watch it over and over. Literally no one and even on this forum, people seem to agree it was a good movie but not all that. In the end, the land will be visual stunning but very little will be able to be done to add to that section of the park if the next film is not sucessful. As I said before if Disney wanted to add a new IP and hit a demographic they are desperate need of that Universal gets (males and teens) Hunger Games would of been a better IP to go with and I have tons of things, Disney could do.
This, basically. There is a definite "edge" if you have a beloved IP. Harry Potter is definitely a beloved IP; Disney has many of them too.
Disney doesn't always make the best use of their IPs in their parks; sometimes they build rides that exploit older IPs that aren't terribly meaningful to a wider audience. And we all know they have a bit of a "boy" problem, especially in Florida where there's no Cars land to appeal.
Disney paid a bloody fortune for the rights to Star Wars. Honestly it's one of the few IPs Disney owns that could reel guys of all ages in. Most of the guys I know who go to WDW are either going with their extended families, or are parents themselves and are taking their young kids. A lot of them have switched to Universal as their kids became teens. They don't see WDW as a "manly" destination, per se, because it's full of princesses and stuffed animals. Except during Star Wars weekends, when it makes them nostalgic for their manly childhoods.
Yeah, I'm married to a man who spent an obscene amount of money in the Star Wars souvenir tent last May. Obscene. Amount. Of. Money.

If they built a Star Wars park with a bunch of proper rides and stuff, he'd want to go twice a year.
I think that what is MOST important to recognize, though, is that when you exploit a well known worldwide-beloved IP like Star Wars or Harry Potter, you have the potential to draw in guests who normally wouldn't think of vacationing at a theme park resort. You are expanding your audience beyond those who are watching Disney animation with their little ones, and that's a good thing.