An interesting article from The Register today about the IBM processor roadmap and also some possible hints at whats going on at Apple with regard to PPC...
I think the two most interesting and relevant quotes are:
"The NeXT team who took over Apple in 1997 have plenty of experience of producing one binary for different processor architectures: HP-UX, Solaris and x86 as well as Mach on 68000. NeXT called these Multi-Architecture Binaries, or MABs."
"One glitch in what could be a smooth transition could simply be the amount of legacy MacOS9 code: much of 'Classic' is still written in 68000 instructions. Getting OS X onto a new processor is going to be difficult with so much old code hanging around."
Make of it what you will! :)