PCIe is defined for 1X, 2X, 4X, 8X, 16X and even 32X lanes. The maximum data transfer for 32 lanes is eight Gigabytes of data per second, per direction. Once the industry moves to PCIe 2.0 the amount of transfer will theoretically double from 2.5 to 5.0GT/s . This will enable 16 GB/s transfer and two times 32X PCIe lanes.
As the PCIe migration from 2x8X to 2x16X didn't result in any significant performance difference as this is not the limiting factor, we doubt that 2x32X system will bring any benefit in this direction either. It will be a great marketing point, though, as it sounds twice as good.
The PCIe 2.0 deciders should be ready to decide in 2007 but I guess it's still too early to talk about them. PCIe 2.0 will make Quad SLI/Crossfire possible at 4x16X PCIe lanes as well if you really want to do it. ยต