Would it "quench our thirst" for a GF4, if they just made another mob movie with Pacino/DeNiro, maybe based on the life of a real life mob figure, and not have a sequel, but a whole new mob film???? That way, our favorite actors can be in them and they won't have to spin off of 3 other movies??? Of course, it would be hard to top the GF!!!
"Mankind must put an end to war before war puts an end to mankind. War will exist until that distant day when the conscientious objector enjoys the same reputation and prestige that the warrior does today." JFK
Of course, it would be hard to top the GF!!! 
