A few years ago, before Apple announced the switch to Intel processors, some pundits were pointing to the iPod and predicting that it signaled the impending end of the Macintosh computer platform.
The pundits said Apple was refocusing its business and moving away from general purpose computers towards smaller gadgets with higher profit margins. They were partly right, in that Apple has gotten into that business in a big way (and we probably haven't seen the whole picture yet in that regard), but they were wrong in that the manner in which Apple has chosen to do so reinforces the Macintosh rather than undermining it.
While the iPod was initially too limited a device to handle in this manner, more recent gadgets, the Apple TV and iPhone, run versions of OS X. Exactly what this means is confidential, but it's clear that major components of Mac OS X have found their way into the newer devices in quite recognizable form, and that any extensions and optimizations developed for these devices are very likely to find their way back to the Mac, where applicable. It's also clear that there is a much closer association between OS X on Apple TV or the iPhone and Mac OS X than there is between Windows Mobile and Windows Vista, which don't share much more than a name.
Now, rumor has it that the iPod is about to come full circle, that the new iPods to be announced this Wednesday (9/5) will also be running a version of OS X, likely one quite similar to that which runs on the iPhone.
This means that, with the exception of AirPort Express and the possible exception of AirPort Extreme, Apple's entire product line will be based upon the same collection of computer code. Not every aspect of that code will apply to every product, but there will be basic components that apply to all, and others that need only minor specialization.
While this sounds a little risky, like putting all your eggs in one basket, it does mean that Apple's focus is on OS X, that there are multiple payoffs for Apple in putting further effort into its development, and that there is good reason to expect Apple's products will work together seamlessly, since they'll all draw from the same codebase. In particular it means that Apple will be able to bring new products to market with a minimum of effort, since much of the software will be off-the-shelf.
This is about as close to a guarantee that OS X won't become an orphan platform as it's possible to get, although another 10% share of the computer market wouldn't hurt. ;-)