Well it looks like DigiTimes has shed some light on SIS and VIA plans for the DDR400 market.

"As Intel currently has no plan to launch related products, the roadmap of the new DDR400-based chipset market is expected to be charted by Silicon Integrated Systems (SiS) in the Pentium 4 arena, with VIA Technologies dominating the Advanced Micro Devices (AMD)-platform sector while Nvidia looks to establish a bridgehead."

More information @ DigiTimes.