sounds like it would be true. we met a guy from AST compters in penang in 1991, the ASTs had AMD cpus in it. my dad got one shortly after as did my sis. there good machines. i have made at least 2 amd machinces, when amd was leading over intel in the early to mid 2000s.
they are not currently the fastest, but they are still hell good. and i think it's a bit **** when every thing is compared on to that level. most people don't buy the fastest CPUs anyway. so they would be perfect for an imac or mac mini, or a new range of devices. they are also storming it in laptop gpus. they have bought out some great ones recently.
i would love to have the options of both CPUs. and i think apple could do it in a way that it would still capture a certain part of the market.
i really don't think you'll notice a performance drop. i always found my amd cpus to feel 'snappier' than the p4s. so i would welcome amd cpus. there's nothing wrong with them, and most people don;t need the power.
i am sure if apple can capture a lower socio economic group with cheaper machines, without the CPU delays of intel, i would welcome it. AMD was top of the game at one stage (though unpopular). if apple go with them (and they get a dedicated revene stream) i would be very very interested in what they come out with.