No question about it, Apple's homebrewed processors for the iPhone and iPad are getting mighty fast. According to an analyst quoted by AppleInsider, those chips will get fast enough to power Macs "within 1-2 years," at which point Apple could begin to transition away from Intel.
The analyst, Ming-Chi Kuo of KGI Securities, believes the performance of Apple's chips will land "somewhere between Intel's Atom and Core i3 lines" in that time frame. That seems like a conservative estimate, since Apple's current-gen A8 is already fast enough to beat Bay Trail—and the A8X is even faster. I'm sure Apple will have silicon powerful enough to drive new MacBooks and iMacs by 2017.
Basing those systems on homebrewed silicon would give Apple greater control over "launch timing of the Mac line," Kuo believes, since the company would no longer be tied to Intel's product cycles.
Of course, transitioning away from Intel would involve some compatibility headaches. (Remember, Apple's A-series chips are based on ARM's instruction sets, not x86.) The move may also make it more difficult to dual-boot Windows and run Windows games, which would be an obstacle for users who want the best of both worlds. Apple is becoming a force to be reckoned with in the semiconductor industry, though, so there could well be some upsides for users on the performance and battery life fronts.