The movie will end before the two-year time skipSince the movie will cover the first half of the book, it's likely that it would end around the time Jessica drinks the Water of Life and Paul chooses the name of Muad'Dib. In that sense, the second movie will show characters like Feyd-Rautha, Alia, Emperor Shaddam and Irulan.
The Emperor will appear if only briefly in this movie, and will be a returning cast member from the first movieIf this movie does only cover the first half of the book, we will still need to see the Emperor of the Known Universe at least once. The Emperor will be played by Sting.
Duncan Idaho will survive the initial attack on the Atreides, only to die defending Paul and Jessica.In the trailer, he addresses Paul as 'my lord duke', implying that Leto is dead.
The Padishah Emperor will not appear in this movieTo simplify storylines and save on people they have to cast in the first film, the Padishah Emperor and whoever plays them (not to mention Princess Irulan) will not appear until the second film of the duology when they arrive in response to the Fremen uprising.
Duncan Idaho and Gurney Halleck will switch fatesSince trailers show Duncan addressing a desert-bound Paul Atreides as "my duke", it stands to reason that he gets at least a temporary Spared by the Adaptation versus his book fate of dying in the Harkonnen attack. Conversely, to keep the stakes of the battle closer to the book, perhaps it is Gurney Halleck instead who gets a Death by Adaptation in the Harkonnen/Sardaukar assault.
Rabban will die and Feyd-Rautha will just replace him for Part 2Of note is that there's been no word of Feyd even being cast yet. If a second film gets made, Rabban's supposed to die during that. But perhaps they will kill him off early, say at Duncan's hands, to set the stage for his brother's entrance. Alternatively...
Rabban will take over Feyd's role completelyPerhaps there's been no news of Feyd being cast because they don't plan on including him. But this would be a letdown for various reasons, not the least being that a Chalamet vs. Batista death duel would seem so lopsided on the surface in Batista's favor that Chalamet would have to win by the rules of tropeland. This wouldn't feel so telegraphed if Paul was facing someone who looked like his equal.
- Not including Feyd in the movie, if they intend to have a second movie, wouldn't make sense particularly when the Bene Gesserit's Kwisatz Haderach plan is going to be revealed in the movie and that plan is essential to the overall Dune saga and Paul's character. In their plan, Feyd is supposed to wed Leto Atreides and Jessica's daughter and their offspring would be the Kwisatz Haderach. But since Jessica bore a son instead out of her love for Leto, the Bene Gesserit's Kwisatz Haderach plan fall apart. Also, Feyd is Baron Hakonnen's favorite over Rabban and is the heir of his house, making him much of a Foil to Paul. And given Batista's age (he's in his fifties), if they intend to make Rabban a Composite Character of Feyd, the implication is there... but again, the director is not going to do the same stunt Jodorowsky is going to do in his proposed movie.