We don't know if they're extinct or not, they very well might not be. I guess we would have to visit Scranton to find out.
You seem to just be hoping the family isn't gone. They haven't been on any list of current viable families from the FBI since the 1980's. And that was the last time there were any significant cases involving the family. D'Elia is said to be the last surviving member. All the evidence is there to show the family is no more. Just accept it.
