A lot of people thought the ending to Pirates III was detracted from by the scene in which Barbarossa and Jack head towards the fountain of youth. It lessened the finality of the movie.
Who cares? The movie, despite being the third and final in the series, wasn’t supposed to be final. Jack Sparrow wasn’t simply going to end his piracy. The scene left an opening, both for another movie (unlikely, but possible), and in the viewer’s imagination. Instead of sitting still for the end of the movie, in the viewers mind leaving the theater, Jack is already headed out for destinations unknown. Thar be adventure in these waters, rather than doldrums.