I can understand why LucasFilm didn’t want to tho. I imagine George’s original outline for Episode 9 probably concluded the entire Saga, and LucasFilm and Disney are not out to end the Star Wars story.
I’m interested in how they would even do a fourth trilogy. There likely won’t be any more Skywalkers by the end of IX, and I don’t see how they can make another mainline trilogy without them.