Maul surviving is so dumb even George Lucas couldn’t have thought of it. The dude was literally chopped clean in half. That alone is enough to kill anyone instantly. Never mind the fall down a bottomless pit. I don’t care how strong with the force you are, what kind of alien you are, it’s just dumb. Boba Fett surviving, I can see. We don’t really see what it’s like inside the Sarlaac so it might be possible for him to find a way to cut himself free and jet pack out of there before he gets digested. But we clearly see Maul’s body break apart and watch him fall down an endless shaft. You might as well say Palpatine survived too. I mean why not? Hell, Darth Vader already survived burning once for that matter; who’s to say he didn’t survive being cremated? Maybe the ghost was just an illusion. I mean we never saw him fade away like Obi-Wan and Yoda did. And you can definitely expect to see Han return in the next movie.