While initially it seemed that director Denis Villeneuve would be stepping away from the sands of Arrakis for a while following the release of Dune: Part Two, he has since confirmed he'll be working on adapting Frank Herbert's next book, Dune: Messiah.
Now, as per Deadline, it seems that things are moving very quickly to get Dune: Messiah started. Filming will apparently begin this June, rather than starting in 2026. Considering the film's prospective release date puts it in the middle of December next year, this gives plenty of time for production and post-production, unless Villeneuve really goes all-out with his effects.
This will be the end of Villeneuve's trilogy, as he sees it as the end of Paul's story in Dune. However, considering there are more books in Herbert's universe, perhaps we'll see some other director step onto the sands of Arrakis in the future.