Knowing Gotti as we do, I think he would have cut his throat before giving the Feds the satisfaction of turning him. He would rather go down in history as a stand up Boss. Also,being that he wanted Junior to be acting Boss,he might have figured that control of the Gambinos could stay in his family if he wasn't tarnished by a snitch jacket.Or maybe he thought he could pull a Persico and stay Boss while behind bars.