There are already SSDs made with PCI-e interface for 2GB/s+ full duplex bandwidth, actual speeds 1GB/s+. But these are expensive enterprise class products, not available for mortals like you and i. But this kind of technology could be commonplace and would be logical for the system disk. See here for an example:http://en.expreview.com/2009/06/06/super-talent-shows-off-its-super-fast-pcie-ssd.html
But chipsets with 6Gbps SATA and also USB3 (10 times faster than USB2; 4,8Gbps) are coming with the next generation AMD 800-series chipset, and nVidia/Intel will likely follow. Another feature is Powered eSATA, removing the need for seperate power plug for eSATA devices. One cable supplies both data and power.