When they really need to. But they'll fight it hard! Apple's business model is to lock everything down -- very closed indeed. This does not align with the goals of bitcoin, at least, how I perceive them.
I hope Apple will do it but I'm not sure if they accept Bitcoin. Apple has Apple pay, a centralized credit card system and Apple is promoting it heavily. When Apple will accept Bitcoin it would be contradictory because it doesn't support Apple's product.