Disney bought Star Wars. Now they are making more movies, a show, and I’m sure they’ll do some theme park work. Expanding worlds is what Disney does. They take something that’s a story, then turn it into merchandise, write backstories, build worlds that you can walk into.
There is plenty of room for this from others, but yet it’s the most common from Disney.
Is there a world that exists today that you could expand? Perhaps a book you enjoyed? Or a movie your friend made?