I wanted to post this comment on Seth Godin's blog. In this post, Seth was watching people in a Starbucks shop, and out of five people owning a laptop, five of them (or a 100%) were using a Mac.
We all know that Apple likes to be different (the famous "think different" slogan).
So what happens while the extravagant becomes the standard? That means that the deep position of the Apple's brand change. You can't say I am different, I am standing out while you are everybody...
In my opinion, this is not that bad. Let's not forget that a brand is based on the public image of a company. Apple will have to change its position, its way to market, but its customers will have already perceived the change and already change their idea of the brand. The real challenge is indeed being able to let the communication evolve.