I disagree with this completely. Apple focuses on the Teen and College markets, which are style, fashion, and image focused. This will keep them at the top for a while. At some point Apple's disregard for cost, technology and reliability will cause them to fall out of favor. Once that happens, it will be a free fall because Apple does not have any other base to fall back on, like in the past.
Now with that said, the new Mac Pro might start recreating that base, provided the new Mac Pro does not have the problems that other recent technology releases have, is upgraded more often, and a middle ground Mac is released between the mini and the Mac Pro.
I am not holding my breath, because Apple management's DNA for good products has gone out the door (outside of the iPhone and a heavy image focus).