Apple jumped off of NuBus when PCI overtook that less used standard, it jumped off of SCSI when IDE overtook SCSI for small computer use, and now it's doing the same for its processors as the heat profile of Intel chips actually is looking better than PPC. Wow, reasonable engineering decisions like this is going to make it really tough to sustain the "Apple is a cult company" meme.
One of the really good thing about Apple's hardware is that it used a reasonably sophisticated firmware system, IEEE-1275 or Open Firmware. One of the unresolved issues of the coming new hardware designs from Apple is whether they are going to continue using IEEE-1275 (and thus keep Mac OS X only for their own hardware) or they are going to also shift over to Intel's BIOS replacement, EFI which should mean that any competent EFI geek should be able to make hardware that OS X will run on. That's a big deal because it would mean that Apple sees more profit in shipping $129 boxes of OS X consumer and $999 boxes of OS X server than in shipping Xserves PowerMacs, iMacs, etc.
If this is the case, this is a huge announcement to the entire PC industry that they've been commoditized and the Dell model of cost reduction is king. Apple's exit from hardware would mean that innovation is dead as a business model for major PC manufacturers. The only point of competition would become in software and services.