It's easy to forget just how important the iPhone is to Apple's business. Nick Wingfield writes a great(and not too long) piece for the New York Times, giving a quick "state of Apple" and update showing where the company is today. This is my favourite section:
Underscoring how drastically Apple’s business has been transformed by mobile products, revenue from the iPhone rose 56 percent to $17.13 billion, making up 48 percent of the company’s total revenue.
Firstly, revenue from the iPhone rose 56%, year over year? Holy shit.
Secondly, the iPhone is 48% of Apple's total revenue? That's a lot.
I'd suggest that data point alone is almost enough of a reason to suggest Apple will be eager to release completely new products; perhaps they can decrease the importance of the iPhone to their business. One wrong move with the iPhone, and 48% of their entire business could suffer.
Releasing something completely new could knock the iPhone's revenue slice down to a more manageable amount, whereby less growth wouldn't effect Apple as significantly as it would today.