If Vincent Gigante's attempted assassination of John Gotti would have been successful, I think it would have had a major impact on both the Gambino Family as well as the rest of the New York Mafia. With Gotti gone,the Family would have installed more appropriate leadership,and quietly slipped back into the shadows.

Gravano would not have been underboss, and without the Gotti leverage that he provided to the FBI later,quite possibly wouldn't have flipped.

Also, the increased attention that the FBI was focusing on Gotti. as well as the Mob in general, might have abated a bit.

Nothing good came of Gotti's reign and nobody would have been sorry to see him go.