The fastest fix is a very short copyright window, say 5-10 years. Given the fact that every movie release makes back it's entire production budget in 1 week or is immediately deemed a flop, 5-10 years is plenty of time to mine an IP for boatloads of cash, plus once anyone can make a star wars movie or book or whatever, the real value shifts instead to the brand that produces it. New brands can make a name for themselves respinnong "old" IPs and making far better content than the original studio would've been willing to risk, and big brands can focus more on how important it is to view the only official versions of a given IP based on their branding.