Board Thread:Theories and Speculation/@comment-30355627-20161218164138/@comment-1512913-20161220232214

Sasuke deactivated it as well in The Last, unless you count it as a mistake. To me the connection between Sharingan and Rinnegan is simple, they are sibling genjutsu with Rinne Sharingan as the parent.

Lets say Sharingan is son and Rinnegan is daughter, to each other they are brother and sister. They are not part of the same line in a one becomes the other sense, but they share a common ancestor.

Saying Sharingan can/does evolve/devolve into Rinnegan or that Rinnegan evolved/devolved into Sharingan is wrong. There is no evidence for that whatsoever, it was only Orochimaru and Kabuto's hypothesis which said that what lies beyond Sharingan is Rinnegan, as in that the former can progress into latter, but it was just an educated guess. nothing factual. They most likely came up with such a hypothesis for few reasons: So it would seem, their train of thought was: 'if this is all true, then perhaps merging the powers of the offspring could recreate the Rinnegan'
 * they might have known or believed that both Senju and Uchiha are descendants of Sage of Six Paths
 * Sage of Six Paths was rumored to have had the fabled Rinnegan

And it 'proved true' (not really, it was because of reincarnation business, not just a Senju+Uchiha merger) or rather it appeared as such, when Kabuto recreated Rinnegan in Edo Madara. So to him it must have looked like Madara's Sharingan became Rinnegan, but it really didn't. The Rinnegan just appeared besides the Sharingan.