Makes sense. With a billion devices out in the wild, Apple's huge challenge is making each one a vending machine for Apple services like iCloud and Apple Music. Here's Cook's actual answer in the widely read Washington Post interview from yesterday:
How do you make the case that Apple is still a long-term growth company?
In today's products we have services [iCloud, App Store, Apple Pay and the like], which over the last 12 months grew about $4 billion to over $23 billion [in sales]. Next year we've said it's going to be a Fortune 100 company in size.