Saw it, loved it. Some of the best Sci-Fi put to screen. Denis is head and shoulders above the rest of the directing dross that still get insane funding these days.
But I 100% agree with Denis wanting to stop at Messiah. His approach to movies, the realism, the grounded reality of the world/universe just cannot put the other books to film. They are bat-shit wild. People will laugh them out the theatre. His style of world building and story development made Part 1 and 2 seems almost docu-series in it's approach. It all feels real.
I think dune as a book series works for a lot of Sci-Fi nerds because written text is interpreted in the brain, we visualise it internally, it's not shown to us. Children, God Emperor, Heretics, Chapterhouse are niche scifi. I think the messages from the series would be fantastic to see on Sci-Fi cinema, but say Denis was to take ownership of that interpretation onto the screen. He would have to fundamentally change so much of the series to keep in-line with his directing style and approachable to the general masses. Stopping at Messiah and then introducing the masses to the books as a whole is a win in my eyes.