Numonyx -- a joint venture between STMicroelectronics and Intel -- has already commercially shipping PCM devices code-named "Alverstone" in small numbers. Samsung and Numonyx earlier this year announced the companies would jointly develop PCM specifications.
There are other technologies beyond PCM being researched as an alternative to flash memory, including MRAM (magnetoresistive random access memory) and RRAM (resistive random access memory).