Speculation that Samsung, TSMC, and GlobalFoundries could all supply Apple with its next-generation processors suggests that a wafer fab in the US and a willingness to guarantee preferential access may be key factors in negotiations.
The third piece of evidence is that GlobalFoundries is being cut loose by its owner, Advanced Technology Investment Company (ATIC), a financial vehicle of the Abu Dhabi government, with the possibility of an IPO as a means of allowing Abu Dhabi to reduce its ownership. (See Globalfoundries eyes IPO as ATIC sets expectations.)
GlobalFoundries, a relative newcomer in the foundry business, has a newly commissioned wafer fab in Saratoga County, N.Y., that has a budgeted cost of about $5 billion so far, but GloFo does not yet have the large number of clients that TSMC has. There has also been discussion about whether the likes of Apple and Qualcomm should, or would, move into chip manufacturing.
The fourth piece of evidence, from August 2012, is that TSMC rebuffed both Apple and Qualcomm when each offered more than a $1 billion to obtain a dedicated supply of processors.
One can imagine that $1 billion offered to GlobalFoundries would evoke a different response, and then Apple would not need to wait for a couple of years before being able to make claims about repatriating at least part of its manufacturing supply chain to the United States.
It is also worth mentioning that GlobalFoundries' links with IBM as part of the Common Platform Alliance means that its CMOS manufacturing process is closer to that of Samsung's than that of TSMC, making a transition of processor circuit design elements slightly easier. But to be honest, the imminent moves to FinFET construction are likely to make such things moot in the longer run.
The only thing that counts against GlobalFoundries is that, being a newcomer with a new US fab, it has yet to build up a long track record of consistent, successful execution. This is one reason Apple would not wish to have all its processor eggs in one foundry, as it does now with Samsung.
This argument would suggest that Apple should make some processors with TSMC, some with GlobalFoundries, and could even let Intel into the discussions. At the component level, Apple has always operated a buying policy of playing the field and keeping suppliers keen. I see no reason to think it will not do the same at the foundry level.