One other almost hint- right before Itachi died, his last words were "...my eyes, my eyes..." as he stumbled towards Sasuke and gave him the forehead poke of death. Now Sasuke's eyes are suddenly capable of Mangekyou Sharingan. What if Itachi wasn't referring to Sasuke as his personal eye farm in that last moment, but was actually, in a way, referring to transferring his eyes and their capabilities to Sasuke? (If it turns out Sasuke actually already had Mangekyou [doesn't think he did but isn't completely certain], please forgive my idiocy regarding the matter).