If Sakura

[AaaaNinja]

It would be like handing over the badguy's final most valuable ingredient into the care of a puppy.

 

[Almighty Ra]

I think Obito is gonna give her something to help in the fight with Madara or ask her to destroy his Rinnegan. Both could help in the fight but the later is more of a monkey wrench into Madara's plans to have both eyes.