Here's my pet theory
First off, the disclaimer: this is my pet theory, i.e., a total, wild, pulled-of-out-my-*ss speculation, okay. I have no inside info or contact with people who might know this, but here is my speculation of why this AMD thing keeps coming up despite the fact that the use of the IBM 970 is almost a certainty.
Put this AMD thing into a bigger context of recent events.
We've heard that 10.3 will include a more integrated Classic environment where Classic Mac OS apps will be given many of the benefits of Aqua.
Apple quietly releases their implementation of XWindows system, X11. Despite the fact that this news set Slashdot buzzing for days on end and probably should have had some mention from Steve Jobs in the keynote he'd given a few days prior, it was released very quietly. Interesting.
Next, the somewhat unexpected news that Microsoft was buying Virtual PC. What on earth could Microsoft want with VPC? We can speculate that they want greater control over emulation of Windows on the Mac, but that sounds weak. They still control the operating system that gets installed on VPC so from that perspective they've gained nothing by buying out VPC.
And then these weird, peristent, inexplicable rumors that Apple is in talks with AMD about something or other. Who knows what. It's very doubtful that it's about a chip that would replace the PPC since we've read many, many well-informed examinations of such a move and the technical hurdles would likely ruin Apple.
So what could all this possibly point to? Apple has given us a system that can basically run software from three different operating systems: the classic Mac OS, Mas OS X (the Next OS), and Unix. They recently brought the Unix world closer with the release of X11. Wouldn't it be amazing if hardware in the near-future included an "add-on" chip (something like Altivec that works in conjuction with the PPC processor) that emulated the x86 hardware? Maybe it would give Mac users the ability to run Windows and PC software, not via software emulation, but with hardware assistance. Imagine the interest Apple could draw if they presented the world with a machine that runs the Classic, OS X, Unix and Windows applications... all in one environment and almost seamlessly.
Now does Microsoft buying VPC make sense? Maybe? Maybe not. Maybe MS Mac Business Unit caught wind of this and wants to one-up Apple somehow. Any thoughts?
AMD would be a likely partner is such a move since one could imagine the problems with Intel assisting Apple with this. If it was popular, Intel would be killing their own business. AMD, on the other hand, wouldn't, if I understand the situation correctly.
Anyway... like I said... wild speculation, but that's what all this says to me.