I can see Detroit fading away along with Buffalo (if they haven't already). Chicago's been in decline since the eighties.
But I can't forsee at any point in the future the FBI getting rid of the five families. They're too solidly entrenched in New York. I could see NJ, New England and Philly all fizzling out.
But you don't get rid of a Family like the Genovese's in a decade or even fifty years. Even the Colombo's will be difficult to eradicate.