naruto does not have blood line limit, but there is something special regarding his chakra.. yamato had mention that naruto chakra can suppress the kyubi's chakra or something like that i forgot edi..
i doubt that there's anything special about naruto's chakra. the reason why his natural chakra can suppress the kyuubi's is cuz only a little bit of the kyuubi's chakra gets into naruto's chakra due to the elephant seal. if anyone else was in naruto's situation it would be the same. now all naruto has to learn is to fully unleash the kyuubi without letting it take him over. of course i think that's bullshit since that just proves that naruto can't do shit without the kyuubi.