No, there will be no happy ending. Paul has a narrative arc in the first three books (Dune, Messiah, and Children) that closely matches the Classic Greek Tragic Hero.
The Rise, The Fall, and I guess the Cameo?
The Hero rises, and then their own hubris causes their fall, and then they show up again, old and broken in someone else's story.
Classic Greek Tragedies also feature the heavy use of prophecy.
The exact story beats might be different between the book and movies, but the narrative arc is the same.
But fear not, if you go far enough into the series there's eventually a happy(ish) ending. A lot a tragedy and horror before that...