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.
Chicago is not even close to being done. They'll last longer than the the Colombos which wouldn't happen for a looooonnngggg time