Not sure where all the hate for PowerPC is coming from. It served Apple well enough until the last year or two. It also is still used by many other companies as well as the POWER series.
The POWER series continues to evolve and now includes VMX (Altivec). The G5 is related to the POWER4. Since then IBM has released POWER5, POWER5+, POWER6, and soon POWER7. It is probably feasible to run OSX on POWER6 but would require optimization for full performance benefits. The cost, heat, and power of just one dual core processor running at up to 5.0 GHz would limit it to servers and workstations. Nevertheless, it is an option available to Apple in the highly unlikely event that they decide to release another PowerPC compatible computer.
So, Apple actually has several options besides Intel including shifting focus away from x86 if there is some competitive advantage to be gained by the switch. Apple could move fairly quickly if not without difficulties to AMD, PA Semi ARM or PPC, IBM PPC or POWER. This is good news for consumers as it gives Apple leverage in negotiations with Intel even if they are not seriously considering these other options.
As for Arrandale, I wonder if Intel could replace the GPU with just a large cache? Could it be done quickly and at modest expense? Perhaps something like this has been already tried in their labs?