True, but let me elaborate.
Unless it's the kernel, one writes to an environment, e.g. Win32. I suspect if MAC OS X was officially ported to Intel, that MAC applications could be ported as well w/o much difficulty. Think of Linux distributions that run on different hardware architectures.
Yes, one writes apps for the OS.
But, Apple presumably would want their OS running on x86, not to be a Wintel vendor. Yes, Darwin runs on x86 and there are rumors that Apple has a version of MacOS running on x86 already. But there are issues like device drivers (some *BSD drivers can be used, but they don't cover everything important), testing, etc.
And there's the important issue of an emulator for existing MacOS X applications - I don't know of a reasonable speed one that exists for MacOS X on Intel (there are a couple that go the other way). They can probably argue that Classic won't be needed any more by that time, but existing customers aren't going to want to give up their software while they wait for Adobe, etc., to port their applications - and as you say existing x86 software vendors may say "just run the Windows verson".
Apple's been through 2 CPU transitions already. In each case they did well, but it wasn't an immediate process and wasn't without pain for existing users.
On the plus side, Apple will have a shot at replacing Windows as the OS on PCs.
Man, that's funny. You aren't remembering OS/2 are you. :-)
<wistful sigh>
MS will still have preloads (except for the ~ 1-few million boxes that Apple will ship each year), and Apple doesn't have the resources to develop all the drivers and cajole all of the hardware and software vendors to support their platform. As Peter says, an x86 MacOS box will be unique if Steve Jobs has anything to say about it.
I still don't think it'll happen - at least not like this (1-2 years in advance). I'm sure that Steve remembers [link|http://en.wikipedia.org/wiki/Adam_Osborne|Adam Osborne] at least as well as Ashton does.... ;-)
Cheers,
Scott.