Apple are in the process of performing origami on Mac OS X, to reduce the disk space footprint of everyone's favorite OS. This effort will be much appreciated by all those who have forgone a spacious hard drive for the tighter confines of a solid-state drive.
But MacBooks are not the only OS X based systems to come with solid-state drives. iPhone and iPod Touch are even more constrained in terms of storage. Of course, the iPhone version of OS X is a very different beast to Mac OS X, and we shouldn't expect iPhone to be running Snow Leopard.
Nonetheless, system components from the Mac, such as QuickTime, have, in some form, made their way onto the iPhone, and it is reasonable to expect others to find there way there in due course - especially once they've been re-factored to reduce their storage footprint.
Next up to make the transition in MacPredictions opinion is Speech Recognition and Text to Speech (TTS). Plenty of mobile phones already boast voice interfaces, but not the iPhone. And it would be a very Jobsian sentiment to say that they held off on introducing this until they'd got it exactly right, and that it turned out they'd already solved it in Leopard in a way that outclasses any voice functionality currently available on a mobile device. The challenge is, of course, cramming such a storage-intensive component into a confined space. And that's where Snow Leopard's refactoring comes in.
Expect to see Job's proudly demonstrating Apple's Alex Voice reading an e-mail at high speed on an iPhone at January's MacWorld.