If Dune became a full-fledged cinematic series going that far into the story, the films would have to incorporate some elements from these later books, if not adapt them outright to complete the story in a satisfying manner.
The author died after Chapterhouse: Dune and that novel ended with a cliffhanger, leaving some of the series’ story arcs unresolved.
So years later, his son Brian Herbert and author Kevin J. Anderson used Frank Herbert’s notes to complete the saga with Hunters of Dune and Sandworms of Dune.
If it’s successful, the mythology is dense enough to extend out even beyond Frank Herbert’s books.