ok i have an idea not really a theory but just explaining how things work itachi and sasuke are both sons of whom? fugaku but who is he really? ding ding the current head of the uchiha clan if tradition continues correctly then sasuke and itachi are possible relatives of madara himself.. now this brings me to the eyes sasuke and itachi both have what? amatertsu tsukiyomi and sussano right? except sasukes tsukyomi or GENJUTSU is weaker then itachis which brings me to blaze release sasuke was said to be even better than itachi in amatertsu since he can actually manipulate the flames this is proven as sasuke has been proven to be less proficent in genjutsu or tsukiyomi since he cant slow down time in it.. but both have very similar final sussanos dont they? http://narutobase.net/manga/Naruto/552/2 http://narutobase.net/manga/Naruto/484/9 i could bet that madaras MS sussano was the same way until he got ems with no practice sasukes automatically took a badass upgrade no work required as sasuke gets accustomed to the eyes http://narutobase.net/manga/Naruto/574/15 so im guessing with practice and battle experience sasuke will gain a perfect sussano as well kaumi is a techinque that could be from a branch family of the uchiha just how the hyuga are branched the uchiha may have something similar the most direct bloodline recieves sussano and as you get closer to your ancestor (madara) your sussano progresses further just a theory