Yeah, I think probably after FFC dies Paramount or Sony or whoever owns the rights will do a reboot/reimagining of the franchise.

2022 will be the 50th anniversary of the film franchise; I could see some kind of reboot/spinoff project being done, possibly with the 'endorsement' of FFC if he is still alive.

I could see maybe an "alternate universe" approach being taken to any hypothetical reboot: focus on time-frames not already covered in existing GF films.

You could have one film focus on "The Happy Years," 1927-41, when the Corleone empire grows into one of the nation's most powerful, and another one on "Estrangement in the Sixties" when the relationship between Tom Hagen and Michael deteriorates, and finally "The Corleones in Twilight," 1980-1997, with the aftermath of Mary's killing.