The Gambino family would have to be pretty desperate to let him back into the family. I agree with Ricardo, Gotti would have to be very unpopular. I'm not sure if he is that unpopular.
Gravano would probably kill everyone whether it was in the Corleone family or Gambino family. With Gravano running the family there would be no rules. Every time someone would ask to kill someone, Gravano would automatically sanction it. Forget About It, maybe you should write to Gravano, his new address is easy to find. I'm sure Gravano could tell you how things would be. Remember, he did want to start his own family in Arizona because he "owns Arizona." That's an important fact too.

People can change!
"A f****in jerk like me. Never had nothing in my life. That's not John Gotti. At least I hope that's not me. Maybe I see myself in a light that I'm not in, I don't know."-John Gotti about greed
"We only kill each other."-Benjamin Siegel
"There's no such thing as good money or bad money. There's only money."-Lucky LucianO
R.I.P Mr. Gotti