Our Chinese colleagues managed to get a picture of the motherboard that can accommodate four graphic cards and you can take a look at it here. This is something that you will see toward the end of the year if not even alter.
For the ones that plans to get new Nvidia two by 16 PCIe slots Nforce 4 motherboards you can expect that such boards might be able to accommodate two Asus or Gigabyte dual GPU cards. You can find some details about the Asus Geforce dual 7800GT card here.
Full story at the Inq.
Some pics at HKEPC (Chinese).
Looks like the upcoming 90.x Deton^H^H^H^H^HForceWare drivers might support this in two ways: Either by running 4 videocards on such rare boards as the Gigabyte GA-8N SLI Quad Royal, which provides 4 x8 PCIE slots, or by running 2 dual cards like the Asus Extreme N7800GT Dual (although these dual cards do not yet provide an SLI connector) on 'SLI32' boards or even, presumably, on any old SLI rig.
Uses other than bragging rights or space heating purposes?