There was an interview where he said he wanted to adapt Messiah as a third film

https://nerdist.com/article/dune-movie-trilogy-messiah-denis-villeneuve/

Villeneuve revealed that he has envisioned not just a two-part adaptation of Dune, but its sequel novel Dune Messiah as well. In response to question by Screen Rant‘s Ash Crossan, Villeneuve said, “The thing I envision, the adaptation of two books, Dune and Dune Messiah. We decided to split the first novel in two, so now we are at three movies. Those movies are very long to make. For my mental sanity, I decided to just dream about three movies.”