I think Hyuuga is even an older clan than Uchiha and Uzumaki/Senju, may be the oldest clan in the Narutoverse. That is why it was said to be the Konoha's oldest and greatest bloodline. I'm pretty sure most people would think that it is bullshit that it is the greatest bloodline, but when we speak from the fact that Sharingan has a certain darkness to it and the history of how the Uchiha was wiped out from the village, it would be logical for Konoha to acknowledge it as its greatest bloodline. When you think of it like this (Hyuuga being the oldest clan in the Ninja world) it is never impossible that the Hyuuga bloodline is somehow tied to the evolution of Sharingan and Rinnegan. Kishi may go this route (as suggested by the OP), if only to tie some loose ends about things implied earlier in the manga.