TCTTS said:
Two films.
Ah, that changes my perspective a bit. The first film could afford to be a cliffhanger and basically end just where Book II ends.
Also, is there a more perfect project than this to use the BttF2/3 post-credits preview of the sequel? Finish Dune 1 on a cliffhanger note, run the main credits with a countdown clock in the corner, then give a selection of shots from Dune 2 to pump everything back up. Maybe even make it a Star Wars-esque behind the scenes featurette like they show at Celebration.
Countdown ends. Black screen, with a barely perceptible but growing sound of a thumper in the darkness, then like 3 minutes of action shots from the sequel set to what I assume will be a kick-ass theme. Last shot is Paul standing his ground before mighty Shai-Halud.