Obviously, we can't know the future, and regardless of any fears, there will be ups and downs in the future of Disney parks. The problem is- this is a huge step in the wrong direction.
In the last decade- real competition for Disney parks have emerged with what Universal's been doing- and will continue to do. Disney isn't the clear cut leader in the industry anymore, they have real, valid competition in Southern California.
There's also been a huge emergence of themed entertainment fans of the industry and art- that extends beyond Disney. People out there (Matt Quimet for example) who really understand what makes themed entertainment great, and how to maximize the park experience. From what I understand, Knott's has been making strides in improving the park under Quimet's leadership.
Even Six Flags is working on making Magic Mountain an actual vacation destination- slowly but surely they've been fixing up the park, extending operating hours- and working on making the park an actual pleasant experience. The Justice League game ride they put in was a huge step in the right direction for them, and while they have a ways to go, I'm excited to see what they do in the next 20 years.
Gone are the days where Disney can do literally anything they want, and still be ahead of the competition. In such a cut throat industry- they really need to be hiring management and corporate leadership who love the parks and themed entertainment, and understand what makes it work and how to progress the parks- while respecting the history.
Or, they can combine the parks with consumer products- which gives off the impression that to Disney, the parks will continue to devolve into a pure marketing ploy for whatever hot property Disney has.