There is a rumor going around that Apple is (again/still) considering switching to its own ARM-based CPUs in at least its lower-end Macs.
First, consider that platform independence was one of the primary touchstones in the development of OSX, and, from the beginning, Apple maintained parallel PowerPC and Intel builds, for something like five years before finally deciding to take the plunge, driven, in the end, by IBM's unwillingness to continue to invest in energy-efficient consumer versions of its POWER architecture, and Motorola's disinterest in what they viewed as a niche market and heavy investment (eventually leading to heavy losses) in Iridium.
Driven by the need for reasonable performance in a very low energy package, Apple has developed its own line of processors, based on ARM, which they've made and sold by the millions, packaged in iPhones, iPods, iPads, AppleTVs, and perhaps even Airport Extremes. Because it owns the designs, the marginal cost of each additional unit is very low, and it's likely that they can assemble a circuit board bearing four, six, or even eight of their own A-series chips for what a single Intel processor costs them.
That Apple would maintain a parallel build of OSX on ARM is practically a given. Of course they do, and would have been doing so from the moment they had ARM-based chips that were up to the task.
Does the existence of such a parallel build mean that a switch to ARM is imminent? No, but Intel had better watch out that they don't try to maintain profitability by hiking the prices of their processors even higher, because it's very possible that they've already passed the point where Apple could get better performance for less money by using several of their own processors in place of one Intel processor.
And, don't forget that Apple has been through such a transition twice before; it would (will?) be as seamless as possible.