1. Perhaps after this conflict ends, Sasuke will gain Madara/Kaguya's Sharinnegan, and Naruto will gain the full chakra of each of the Bijuu (thus consolidating the powers for their final fight).
2. However, as it stands, Naruto and Sasuke each powered-up half their bodies... Sasuke has a Sharinnegan on the same side as his Crescent Moon left hand, and Naruto performs Bijuu-augmented Rasengan / Senjutsu healing jutsu with his Sun right hand. Together, they are symmetrical, apart they are each asymmetrical... and I think that's the parallel Kishi is trying to draw. They have been "linked" in one way or another to complete each other. I believe that link was through Ninshuu, as the SO6P's attempt at showing the power of teamwork.