Sisir Koppaka has written a nice article on what the A7 and M7 (and Apple's custom hardware design more generally) may mean for new product categories.
I don't believe Apple added 64-bit support to iOS 7 and all their apps just to prepare for an eventual transition to 4GB+ memory capacities in future iPhones. I think this was to do with something more impending. Do we know any product category that Apple would be interested in, that would require the use of both iOS and an A-series chip that is 64-bit capable in order to address 4GB+ memory?
Apple TV (the one that is yet to come, not the one that exists).
The new CoreMotion Framework for iOS 7 adds a step counter and a motion activity detector (stationary, walking, running, vehicle or unknown). We know that Apple has been hiring experts in noninvasive blood component measurements. We know they have a patent on a wrist watch. The iWatch must not be far away.
My guess is that the iWatch will not be a iPod Shuffle or Nano like device in terms of an embedded operating system. It will be based on iOS, possibly to allow for apps in the future.