Board Thread:Theories and Speculation/@comment-30631705-20161130044038/@comment-25122992-20161130122957

Itachi's statement about the need of Amaterasu/Tsukuyomi for Susanoo awakening was already retconned by Sasuke's own words. He said that you just need to have a double MS (i.e. possess both MS) to awaken it. Also, Sasuke still has 2 powers of his MS, the first being Amaterasu (left eye) and the second being Kagutsuchi (right eye), with Susanoo as the "third" power.