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.
Only when governments say that bitcoin is a legal tender and it can be used as means of settling your payment is the day apple could go for accepting bitcoin payments. This is very less likely to happen in next few years.