Jason Snell wrote a thought-provoking article in Macworld about exactly how configurable Apple will make future MacBooks and MacBook Airs. In short, he thinks our options will be limited and that is born out by the currently shipping MacBook Airs that will let you pick RAM and Storage levels but offers no configuration as to the processor.

I agree with Jason. Particularly if Apple moves the Macs (or some portion of the Macs) over to ARM processors, I believe they will be treated as appliance computers more than ever before. Consumers buy iPads and iPhones without considering processor (or RAM!) customization and I think Apple would love to pull off the same trick on the Mac.