Why would they want to do this? Intel is ahead of everybody else in terms of process technology, this gives them a huge advantage in terms of power consumption, speed, and heat. I just can't see how an ARM chip manufactured at TSMC or Samsung would give Apple the same kind of performance in the same power envelope. Though GF may be amenable to a new customer, I don't think Intel will be too happy selling manufacturing capacity in their fabs to Apple when they just kicked them out of their market. Though, to be fair, NVidia's roadmap for ARM chips is very aggressive.
Also, wouldn't this mean having to port OSX into ARM as well? I don't know what happened when they switched from Power to x86, but is this difficult, or just a non-issue?