Its like a 80% garrentee that sasuke will get mangekyou sharingan... (That is my estimate)

1. In the old legend there is 3 gods. amatseru, tsukyoumi, and soousano (I can not spell for shit). Mangekyou sharingan's special ability is also named after those gods. Genjutsu Amatseru, ninjutsu tsukiyoumi. however there is only 1 missing. taijutsu soousano (This is a theory)

In the legend it says soousano kills yamato no orochi(orochimaru) and pulls out "Grass cutter"(ktsuangi something). I BELIEVE that this is the fate of sasuke and orochimaru.

Sasuke will Kill orochimaru and gain his sword. in doing so he will develop the third mangekyou sharingan techneque, soousano.
Also soousano is the god of thunder or ligntening (i think raiden was the other guy). This is why I BELIEVE that the mangekyou sharingan move will incoroporate both chidori and the "grass cutter sword" and that will be used to kill the blind itachi

ofcorse THIS IS ALL THEORY. but I AM 80% positive that this will happen