If he lived long enough to flip, I think the FBI would have tricked him in the same way they did trick Casso, meaning they would have gotten every possible information from him and then would have found an excuse to break the plea deal and give him a life sentence. Otherwise, it would be too dangerous for the society to let him out on the streets again.

Willie Marfeo to Henry Tameleo:

1) "You people want a loaf of bread and you throw the crumbs back. Well, fuck you. I ain't closing down."

2) "Get out of here, old man. Go tell Raymond to go shit in his hat. We're not giving you anything."