Does it have to be IPs though? Sure, IPs serve a distinct purpose: to attract visitors with something they are familiar with. And that's almost all Universal has done because up until recently, Universal has had a hard time attracting people.
With Disney's future including Frozen, Avatar, Toy Story, and Star Wars, is that the end to non-IP attractions? If I wrote a list of my top ten favorite WDW attractions, I'd bet fewer than 3 of them were based on an IP.