Board Thread:Rebirth: Story Time/@comment-4869113-20141109220441/@comment-2185383-20141109224942

Either Seireitou or BC.

Seireitou could possibly plan to kill them behind the shadows to make sure his sengoku rebirth isn't stopped by the likes of Naruto and Sasuke possibly for his doujutsu (adding the Sharingan and Rinnegan to his Byakugan, he basically has the three great doujutsu).

Black Crown possibly wants the chakra of the tailed-beasts that's inside Naruto and Sasuke's Rinnegan to facilitate the rebirth of the Shinju (if that's their goal).

Or something else even more interesting. Having them sacrifice themselves to undo a freaking genjutsu seems like a waste to me.