There's speculation that Apple has been looking into using TSMC to source their next generation A6. Apple would have to port the IC designs to be compatible with the TSMC process which would take some time but is entirely doable with the chip design team they've built up. Although there has been reports that TSMC has been having trouble with quality issues on the 28 nm process which is why we might see Samsung manufacturing Apple's SOCs for a while.

http://www.eetimes.com/electronics-news/4229790/Samsung-ramp...