Apple has a history of creating new hardware products that cannibalize its current lineup, and at some point it will probably do the same with the iPhone.
It's already laying the groundwork for the next big thing after the iPhone through its augmented reality (AR) developer kit, which lets developers create apps for the iPhone and iPad that overlay computer-generated images on top of the real world.
Apple hasn't been shy about its bullishness on AR, and by starting a vibrant developer ecosystem now, it puts itself in a good position to have plenty of AR apps ready to go if it decides to release some sort of futuristic AR glasses, as it has reportedly been developing. Those glasses would have the potential to one day replace most of the screens in your life by bringing up anything you want right in front of you. Goodbye, iPhone.
Another big opportunity is transportation. Cook has already confirmed that Apple is working on self-driving technology, which he called "the mother of all AI projects." It's unclear how that project will ultimately take shape. There were reports a few years ago that Apple had plans to build its own car, but those ambitions seem to have been tamped down. The more likely scenario would be for Apple to create an operating system for the car that handles autonomous driving and infotainment centers.
In the end, $1 trillion is just a number. Apple already has the pieces in place to grow well beyond that.
-- CNBC's Sara Salinas contributed to this report.