AMD will stick around, they’re too big to go under. Most of their money isn’t in CPUs, it’s in flash memory. They’re loosing money hand over fist on their CPUs and can’t afford it indefinitely (which is why their new Barton is prices similarily to Intel chips).
Yes, Apple is likely to switch away from Motorola after all of the delays in the G5, but it will probably be to IBM who has an even more advanced process than Intel. IBM has G4 cores running up around 2 GHz, and we all know that the IPC is highest in the G4, not the Athlon.