Nice overview of the IC memory market by Mark Lepedus.
http://semiengineering.com/what-are-fefets/
Gives some very good insight into the challenges that Rambus is facing in its signature market of high volume IC memory interfaces.
Each of these different technologies address different aspectss and different performance market segments. Each of these technologies is likely to require variations in interfaces, signal and control protocol, cost/performance tradeoffs, .different signal and voltage different voltage levels, etc. Far cry from the RDRAM days.