EE Times reports what looks to be a brekthrough in phase-change memory: Samsung preps 8-Gbit phase-change memory. This is a 20nm process, and close to the density of NAND, but they note they are going after a moving target:
The ability within NAND flash to store and detect multiple bits per cell still gives flash a memory capacity advantage over PCM. Flash memory is also expected to go to a form that could stack multiple memory cells vertically, providing further memory capacity scaling.