From Ireland OnLine:
NEC Corp and Toshiba Corp have agreed to jointly develop next-generation magnetic random access memory chips, which are expected to greatly reduce power consumption for personal computers, cellular phones and other portable electronic devices, the Nihon Keizai Shimbun reported, citing sources at the companies.
The partners aim to establish mass-production technology by 2005 and launch MRAM as the primary memory technology, replacing DRAMs and flash-memory chips.
....
NEC and Toshiba have already set up a joint task force with 20 engineers from each firm. They aim to establish a production line to work on prototypes at NEC's plant in Sagamihara, Kanagawa Prefecture, by the end of this year.
So its likely that we see prototypes of Mram before Jedec get round to issuing a definitive specification for DDR400
With RDRam being phased out now this will mean all platforms will be DDR until the release of Mram. I doubt very much if any manufacturers will be releasing another memory technology between now and Mram. They are speculating that mass production of Mram will be round 2005 so I suppose it isn't totally unfeasible for another memory technology to emerge in the next few years...