maybe like a part 6 thing, since jonathan joestar, josuke higashikata and jolyne cujoh didn't defeat their antagonists. araki's already done jonathan joestar (in the form of johnny joestar) killing his antagonist from his part and josuke is probably going to kill his antagonist of his part (i havent read up to the latest chapters yet). jolyne is the only one left so part 9 could be set an alternate version of part 6.