The chip is fabricated on 20-nm "class" technology, which typically means a node between 20 and 30 nm. Like Samsung, SK Hynix doesn't go into specifics about the process geometry. However, it does confirm the chip's 3200Mbps transfer rate and 1.1V operating voltage, both of which match the specifications of the competing Samsung memory.
SK Hynix is sampling its LPDDR4 chip not only to its largest customers, but also to major SoC vendors. Mass production is expected to begin in the second half of 2014, and final silicon should start popping up in "flagship mobile devices" by the end of next year. Thanks to Xbit Labs for the tip.