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.
tl;dr Apple = closed. BTC = open.
I think Bitcoin or cryptocurrencies will also be great for Apple's business. I don't see anyway it prevents them from their closed policy as claimed in the post. They only need to accept it as payment method.