It's been speculated for some time that Apple would move its processor production away from rival Samsung; however, concerns over the stabilization of TSMC's manufacturing process had prevented the switch in the past.
"The manufacturing process at TSMC hasn't been stabilized. Considering Apple's previous patterns of adopting qualified technologies, Apple isn't taking risks. Samsung offers better pricing and capacity commitment for the A6 mobile APs," said an official from a different Apple supplier.
Now it's being reported that TSMC will begin trial production of the 28nm A6X processor during the first quarter of this year and if all goes well the company will supply those processors for the iPad 5 and iPad Mini 2.
Additionally, Citigroup Global Markets has predicted that Taiwan Semiconductor Manufacturing Company will be the only supplier of the 20nm process to Apple quad-core processors over the next one to two years. The 20nm process will likely be used by Apple's future A7 processors.