Sigh, the only way Obito can unlock Susanoo is if he steals his MS back from kakashi, and I doubt that will happen. And to all the people who can't comprehend simple manga, you do not need Tsukiyomi and Amaterasu to unlock Susanoo, Itachi was only referring to himself when he stated following those two abilities, a third power came (Susanoo). You do need two powers, a power in each eye to awaken Susanoo, but not Ama and Tsuki.
No one but Sasuke has been shown using Amaterasu, and he sure as hell doesn't have Tsukiyomi. Do you know what Tsukiyomi is as a technique? In order for it to be Tsukiyomi, the user has to be able to control time and space while in the genjutsu, Sasuke has never done that, so he doesn't have Tsukiyomi, and no, it's not a weaker version because the fact still remains that he can't control time and space. Sasuke's techniques are Amaterasu and Kagutsuchi.