A few weeks ago, we learned that Apple would likely abandon Samsung and turn to Taiwanese company TSMC for production of the A6 processor expected to power 2012's iDevices. According to Reuters, Apple has indeed begun "trial manufacturing" of the A6 processor at TSMC. If the company is able to crank out A6 chips quickly enough and with a low enough defect rate, Apple may select TSMC as the sole manufacturer of the A6 chip.
Currently, Samsung is the only manufacturer of the A5 chip that powers the iPad 2. The same chip will likely power the iPhone 5 and the next-gen iPod touch (if there is one). Samsung stands to lose a great deal of money if Apple turns to TSMC for production of the A6 chip that's likely to power the iPad 3 and iPhone 6.
Samsung and Apple have had a falling-out over the past several months over Apple's allegations that Samsung has willfully copied the iPhone's design. Aside from that, the two companies are also competitors in the mobile space, so from Apple's perspective it may not make sense to have one of its competitors manufacturing the silicon brains powering its mobile devices.