I don't think there will ever be new "original" rides that aren't based on existing franchises. It's not a matter of Disney lacking the will or talent, it's just a fundamental shift in the business model of the entertainment industry since the 50s.
The idea now is "synergy," in other words why spend money advertising a movie when you can spend the same money to advertise a movie and a video game and a theme park ride simultaneously? Cars Land was Cars 2, Iron Man is going to match Avengers 2, and so on. It even works in reverse, rides that were just rides for years became movies (Pirates, Haunted Mansion).
Personally, y'know, it's not my preference, many of my favorite Disneyland rides aren't tied to a franchise at all, but there are a lot of them that are directly based on movies and they're great as well.