Oh, no, no, there shouldn't be another "Godfather", the stories in the films are great the way they are. People already think part three isn't good(which is not my case), let alone a part 4! I know Mario Puzo would've liked to see it done, but with all due respect, the saga of the Corleones has been "examinated" as much as it can be.

"...Luca Brasi held a gun to his head and my father assured him that either his brains or his signature would be on the contract. That's a true story. That's my family, Kay. It's not me."
(Michael Corleone)