Think about it. Part VII retold Part I; Parts III and VI cannot be retold due to their main characters (Jotaro Kujo and Jolyne Cujoh, respectively) getting killed by Enrico Pucci's Made in Heaven (alternate universe versions of people who were killed by the stand will not retain their memories from their previous lives and seemingly act completely different from each other); Part II cannot be retold since if the SBR Universe did, then it would pretty much be a straight-up rehash of the original Part II since there's pactically no new way that can be retold; and Part V cannot be retold since Dio Brando's SBR Universe counterpart (Diego Brando) died during Part VII, plus there's no vampires in the SBR Universe (Dio's vampire-related abilities, such as immortality and the ability to steal someone's body, was what enabled him to sleep with a bunch of people, thus explaining Giorno Giovanna's existence). This leaves Part IV as the only JoJo series in the original universe that can be retold in the SBR Universe (Part VIII is indeed retelling Part IV), which could pretty much mean that unless Araki has something completely new and not something to retell from the original JoJo universe, then Part VIII may well be the last story in the entire JoJo series.