Part of the reason the growth has slowed is that at a certain point, the law of large numbers takes over, and it's hard to grow. Apple generated $35.3 billion in revenue during a quarter when it had nothing new to offer consumers. Which leads us to the other reason growth has slowed.
Apple needs something new. It can't just be another iPhone, or just another iPad. It has to create the next major product category if it's going to get sales and EPS growing once again.