AFAIK, the ASUS P6T7 WS Supercomputer, has four PCI-e lanes, all at full 16x thanks to two NF200 controllers. Four-way SLI was never supported before, because nVidia graphic cards has never been able to support four graphic cards in SLI, apart from EVGA's own GTX 285 Classifieds. They have supported quad GPU SLI in the form of 7950GX2, 9800GX2 and GTX 295 in SLI.
I'm supposing the P6T7 has only been announced as four-way SLI with a BIOS update because recently the GTX 470 and 480 have been announced as four way SLI capable.