polanski's film version of macbeth

The ending of Polanski's film is very different from Shakespeare's play. I think that Fleance going to visit the witches implies that Fleance will follow in Macbeth's footsteps. Fleance will try to assassinate King Malcolm the way that Macbeth killed King Duncan. The cycle of violence will not end. Although, Macbeth went to the witches' coven late in the play; even though the witches declared a meeting with Macbeth in the opening scene & they met him in act1 sc,3. In Polanski's film, Fleance visits the witches, but there is no suggestion that the witches decided to meet Fleance or actually met him previous to that. Also I think that Polanski ended the movie like that because he wants the people watching it to question what is going to happen next. I think he did it because he wants everyone to think that Fleance went to the witches to know what is going to happen now that Malcolm is king.