Disneyland was "inspired by" many Disney movies, there were even intentionally small ride-throughs of those stories. But when it came to the big guns, the attractions that would drive people into his park on a regular basis, Walt Disney made sure the attractions and adventures were wholly original. Fads come and go, tastes change.
For everyone that says "Star Wars" stands the test of time so well, you seem to forget that between 1983 and 1999, there WAS no "Star Wars," and everyone (except, perhaps George Lucas's accountants) was just fine. "Star Wars" kind of died a natural death. We're not facing that same life cycle with film-based properties today as vividly because of our relentlessly marketing-driven society. Even twenty years ago, film studios were not as "sophisticated" (or obsessed) with focusing on "existing IP." They created new things regularly, and Disney was the best at that.
And during those times, Disney didn't take every film it had made and create an attraction around it, though that's what fans probably wanted. That was the time, for Disney, when the Tower of Terror, the Rock 'n' Roller Coaster, Animal Kingdom, Blizzard Beach, even (for better or worse) California Adventure opened. Disney, as it had since the 1930s, believed in creating NEW entertainment, not just rehashing old ones.
Walt Disney was pretty smart when he said, "You can't top pigs with pigs," but now Disney -- and, increasingly, consumers -- want more of the same. They're like that Tellytubby who screams "Again, again, again!" And they get it.
The biggest problem with this way of thinking is the same problem that so much of the business world faces: Because it works today doesn't mean it will work in 10 years. You say, "People will never get tired of 'Star Wars,'" which to my way of thinking is a little like a 9-year-old boy in 1992 saying he'll NEVER not love Power Rangers. If his parents are wise, they'll say, "Of course you won't," but still steer him to something new. If they're not, they'll load him up on Power Rangers, Power Rangers and more Power Rangers until one day he says, "I don't like Power Rangers anymore." Then they'll look at his Power Ranger-filled bedroom and at their declining pocketbook and think, "Gosh, what did we do wrong?"
As a "brand-management" company, Disney is betting that people will never tire of Marvel, that they can't get too much "Star Wars," that Pixar will always be the most sought-after name in animation, that its "tentpoles" will always be popular.
Guess what? They won't.
And when you pour a billion dollars into creating more, more, more, more, more of it at your theme parks, you're left with rides like the original "Star Tours" in 2006 ... rides that cost a lot of money that are going to be very expensive to replace when people don't fancy them anymore.
Universal didn't quite create the same problem with Harry Potter because once its popularity fades, it will just be another part of the park. They've done the smart thing by driving attendance and getting people to discover the REST of what they have to get them to come back.
Disney's done the opposite: Based on the state of attractions and the insistence on removing parts of the old parks to make way for the shiny new stuff, they're focused primarily on what's hot and new at the expense of everything else. (For instance, look at Pirates of the Caribbean with its now-mostly-meaningless inclusion of Johnny Depp; in another 10 years, he'll feel older than Sigourney Weaver in "Alien" at Great Movie Ride, but to remove him will be too costly, so they'll have an anachronistic ride whose novelty has worn off.)
I'm not suggesting Disney SHOULDN'T pursue "Star Wars" at the parks. What I'm saying is, they're doing so on the theme-park level AND on the corporate level at the expense of creating things that are totally new, uniquely Disney and, as such, impossible to replicate. No one ever has created attractions quite as compelling as Haunted Mansion, Pirates, Big Thunder, Space Mountain or Tower of Terror, to name a few. But "Star Wars" or Marvel would have been JUST as much "at home" at Universal or even Six Flags than it would at Disney.
And Disney's placing a bet that has already been proven to be an unwise one. The long-tail "Star Wars" bet didn't pay off for Lucasfilm itself for more than 15 years, until Lucas revived it with "The Phantom Menace." They've bought some time with the next "Star Wars" movies, but ... what if they're not good? What if the public reacts with a collective yawn the way they just have to "Star Trek"? What if six films in six years proves to be too much of a good thing?
Then Disney is left holding the bag with none of its own originally developed, new "IP" (as everyone likes to call it) -- no "Lion King" or "Beauty and the Beast," no Tower of Terror or Expedition Everest, just a bunch of rides and attractions that people feel are stale and anachronistic.
It's a gamble. Based on past history, I, personally, don't much care for the odds.