Of course it's a bad idea. I always thought III was a possibility simply because of the potential money involved, but I wasn't sure Copolla or Puzo would have been involved. I also felt Michael Corleone was too fascinating a character to forever be left as he was in II.

Those of us enamored with the book knew there were storylines that could be expanded to make good films, but Hollywood has gone to such regurgitation I had no doubt their would be future Godfather films unless the entire Puzo family is very, very wealthy.

A Godfather film without Michael is a different proposition entirely and it would be likely be a disaster. I liked Vincente's character (and Garcia's acting) enough to see pontential, but demands great writing, and even the events in the late 80's and 90's regarding organized crime prosecution, would make Vincent's story seem to be pre-ordained. I even have more reservations about the new book. But if this guy is writing the sequel to The Godfather and ignoring the films (except to avoid contradicting them, as he says in another thread), who knows? I'm not so much hung up about a different actor trying to step into a character portrayed by Pacino, Duvall, et al. But if someone almost impossibly, makes a great IV, no one would be happier than I. The 60's and 70's are available to this storyline. It's is a bad idea to make IV only if they blow it, which there's a 99.9% chance they will.
Having said that I believe there will be more Godfather films made. Hollywood is brain-dead and the Corleone family is entrenched in our culture. Though I have complete reservations, I can see the Puzo's family commissioning of a new book as being it could be the the best defense against potentially terrible future Godfather movies. The author has to ace it, though. What are the odds?