Board Thread:Theories and Speculation/@comment-995176-20141108204910/@comment-1292715-20141110180607

Aka Shi Crow wrote: Cause Sasuke was the only one with Potential to unlock Rinnegan, only the ones with Sharingan can evolve to Rinnegan. In other words, Hashirama could've obtained the Rinnegan had he transplanted Madara's Sharingan.

But back on topic SeraphAngel does have a point. Hopefully the Byakugan will be delved into more in the movie.