Sammy seemingly wouldn't have ever had a clean look at the seat. Had DeCicco followed through with murdering Gotti after that initial year (which woulda been tough considering he got car bombed) Gravano was going to be his # 2, that much was documented. From that point on if Sammy had killed Frankie I think it could have started the 1st Gambino War. Everyone loved and respected DeCicco, he also had the ear of older Gambino's like Piney Armone and strong connections to the other families. That theory aside same goes with Sammy taking out John. Up to being boss John was running the Bergin Crew and the Ravenite Crew, the 2 biggest in the Family. Another hypothetical Gambino War would more than likely have ensued. And if you kill John, where does that end? Right off the bat you gotta kill Willie Boy Johnson Ang, Gene, Junior Gotti, not to mention both Carneglia brothers.