The chances of that happening are slim. Motorola screwed Apple with the G4\'s true but Apple going x86 is a step backwards for them.
The rumors only state that Apple has a fall back version of OSX of x86. They have done this before, a few years back they had project star trek where they ported system 7 or something to x86.
There is another rumor picked up be eWeek that IBM\'s desktop version of the Power4 (PowerPC architecture like the G4\'s) might be going into future Macs, hell those procs are even supposed to have SIMD units similar to the G4 AltiVec units.