Nobody would ever come up with any cool new stories, because it wouldn't be worth doing all that worldbuilding.
I would be watching a great postmodern Star Trek movie with elves and ninjas RIGHT NOW.
We would get to see more crossovers. Captain Kirk would meet Mal Reynolds every day, sometimes twice a day.
It wouldn't matter that much for movies and TV — who wants to see some fan film anyway? — but it would make every book saga endless and sprawling.
Paradoxically, you'd see fewer Dune and Foundation books, because there'd be no money in it.
Remixed and reinvented works would revitalize classic SF — every Heinlein book could have alternate fan edits.
There would be fewer TV and movie sequels. And what there was would be low-budget.
Studios and publishers would be frantically searching for the next twenty-year cash cow.
Surprisingly little would change.
It would be the end of originality in SF altogether. Why bother to create something new when Starfleet and the Force are public domain?
You'd have a million cheap knock-offs, stuff designed to be ALMOST Superman, but still copyrighted.
Sequels, spin-offs and remakes would be rushed into production at light speed.
