Given that most mobile chips are done with the 40/45nm generation still, and we just recently moved to the 28/32nm with the Exynos 4412 in the Galaxy S III and the Snapdragon S4, these plans for an even further die shrink are like music to our ears.
Such 20nm and 14nm chips should push the envelope towards lower power consumption and/or high performance in our phones and tablets again, and the new foundry is expected to start producing the goods towards the end of next year. Samsung makes most of the silicon in Apple's gadgets and its own handsets and tablets, and it is likely to stay competitive with this move for a while now, considering that Intel's new Ivy Bridge processors are done with the 22nm mark, but Chipzilla is still to deliver a mobile solution to match ARM's power envelope.
Of course, the other foundries like the giant TSMC won't just sit on their hands in the meantime, and will likely move towards 20nm next year, so we can again expect big leaps in performance from our mobile silicon each passing generation. For now, we'll be glad if those foundries can deliver enough 28nm chips.