Even if Episode 9 were killer bombad fantastic, I don’t think an Episode 10-12 would be a good idea. But with the Episode 9 we got, it looks like a fourth trilogy would just be at best, a really boring story with characters that were kinda cool in Episodes 7&8 but got neutered in Episode 9, and at worst, literally just a redo of a sequel trilogy.
If we see anything about building a New New Republic while Rey rebuilds the Jedi order (or builds the Schmedi Order or whatever), that’s just a redo of a sequel trilogy, but this time without the OT trio cast. I’m a fan of Episodes 7&8, but if that happened, I’d rather they just decanonize the sequels and not pretend that this trilogy wasn’t a redo. Because they’d have a very hard time convincing me it wasn’t.
The best case scenario I think for a fourth trilogy is if it came out decades down the line, when John Boyega, Daisy Ridley, and Oscar Isaac are very old, and they’d be cameos at best with really minor roles.
I truly think Episode 9 is the last one, though. They really don’t need to make new Episodes like they did before, even if 50 years from now, they run out of stuff to make and want a rebirth of Star Wars like they did with Episodes 1 and 7, I don’t think they need an Episode 10 for that. They can just go out and make a new saga now.