My first SF convention was in 1976 or thereabouts, and Frank Herbert was Guest of Honor. I skipped a whole day of 9th grade and later caught hell from my parents, but it was worth it. [This was the year I failed Typing, which is probably the reason that I'm an Emacs user.]
Frank talked about his recent book Children of Dune, and since this was during the US’s early days of Really Heavy Ecology he talked a lot about saving the planet. I forget the particulars. Desertification, human impact, and how we’ve got to get off of this rock, mostly.
The only thing I remember clearly was when he mentioned there was another Dune book on the way. A bearded grad student next to me muttered, “Yeah, Streetsweeper of Dune” and the people around us laughed.
So it was bad, even then, when he was still alive and actually writing the stuff.
There’s another Dune book coming out, Sisterhood of Dune. These things are being pooped out about twice a year, it seems. I haven’t tried to read any since I threw away my first “Dune prequel” — right now, I can’t even remember the title. The series is dead to me. I wish there was a way I could “negatively buy” a book, somehow push it back in their faces as Do Not Want material.