I think a GF4 will be a disaster, and here's an analogy from the Marx Brothers' career that might explain why:

During their early movie career, the Marxes were fortunate to attract talented producers like Herman J. Mankiewicz and Irving Thalberg. These guys believed in making good Marx Brothers movies, and gathered the writing and directing talent to make that happen.

The brothers' last good film, "A Day at the Races", was the one where Thalberg died during production. After that, the studios didn't care about the quality of the films. They only wanted to use the Marx name to put butts in the seats. The only reason Groucho and Harpo even did their later films was because Chico, a compulsive gambler, was in constant need of money.

That's what I fear what will happen to GF4. The suits at Paramount probably think they can make a quick buck by plastering the Godfather name on some second-rate Mafia story. Do they really care about making a good Godfather movie? Or will GF4 be the saga's equivalent of "Love Happy"?