This is a good question. Although Tony is obviously the boss of his crew and was elevated to "street boss," as Rusty points out, I don't think he ever "officially" assumed Uncle J's position. And Uncle J. had been subordinate to Jackie Aprile. I could be wrong, but I think Jackie was subordinate to some NYC family. So, if you do the hip-bone-connected-to-thigh-bone routine, Tony's probably subordinate to some NYC family, and thus is not a "Don" as we think of Don in the Five Families or Chicago Outfit sense.