My guess is the Italian-American Mafia will still be at the top for a long time to come. But they won't have the complete monopoly position anymore : the Albanian mob is spreading, the Sovjet Jews are still strong, the Irish are still active, Mexican drug cartels are increasingly becoming widespread, Triads are very active, African-American/Dominican/Salvadoran/Vietnamese/Cambodian/Puerto Rican/Hmong/Haitian/Filipino/Native/Somali and Armenian gangs are becoming bigger and more organized, the Israelis and even the Yakuza ( under the Yoshitomi Group) are setting up base in the West Coast,...and let's not forget the Outlaw Motorcycle Gangs or the White Supremacy gangs who some would deem as just a bunch of moonshining rednecks, but in reality they're just as organized and just as dangerous as their 'ethnic' counterparts.
So in short, the power of the Italian mafia will still be very high in the East Coast and (maybe) some parts of the Midwest, but they have been receiving a lot of competition lately.