According to Gravano's book, if Castellano went away for one of his cases Tommy Gambino was going to be acting boss and Bilotti the underboss. In Gotti: The Rise and Fall, presumably according to wiretaps, Gotti was told that he would be part of a three man ruling panel with Gambino and Bilotti.

Based on what I've read about Tommy Gambino, it didn't sound like he was interested in being a Cosa Nostra boss. I haven't heard a single good thing said about Bilotti. And we all know about Gotti. So there was bound to be problems. Gotti being hit or Gotti taking out the two Tommys or civil war.

Either way, it probably would have been best for both of them if they kept their heads down and did their own thing. Wouldn't have got as much money but wouldn't have ended up in prison either.