Horace Dediu argues the new M7 coprocessor isn’t just built for the iPhone:

Hence the question of what is the M7′s job to be done. As part of an iPhone, it does not seem to have one. Saving a bit of battery life is not a job, and certainly not one that needs to have billing in a media special event. The answer must be that the M7 was developed for some other, as yet unstated reason.

Sisir Koppaka digs deeper into such possibilities:

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).

Just a few days prior to WWDC this summer, the Xbox One was annnounced with 8GB memory. The 360 had 512 MB of memory. Earlier in January this year, the PS4 was announced with 8GB of memory. The PS3 had 256MB of system memory.

If Apple were to release a competing living room solution now, as Steve Jobs claimed they had figured out, it would definitely have to have around 8GB of memory (if they were interested in addressing big screen console gaming seriously). It would also likely be iOS, and not OS X, that would be needed. I think that is why Apple just announced full-scale hardware and software 64-bit support, not because phones will eventually have 4GB of memory sometime in the future.

Whether it’s a TV connected device, a wearable device, or something unfathomable, Apple is clearly positioning itself for some interesting future endeavors.