Final Fantasy as a franchise is sort of unique because each installment doesn't require previous knowledge of any other product to enjoy it. Think of something like the Star Wars series of films; anyone attempting to jump in at Return of the Jedi wouldn't have the foggiest idea what was going on. It's less a series more a sort of name that has been stuck onto various RPG's that happen to have common elements, elements that arguably cross RPG's anyway. So while they may stop using the name Final Fantasy, it wouldn't be a great shock if they carried on making RPG's in a similar vein to FF.