The illegal we do immediately. The unconstitutional takes a little longer - Henry Kissinger
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.
Nvidia just released release 80 of its drivers and Nvidia usually releases a new driver every quarter, so I don't think that you could expect to see this driver ready before late this year if not January 2006.
The biggest point is that Nvidia can do it and that this card will win some benchmarks for sure. We can only imagine how much power would such a system draw and Asus had an external PSU for this card. Will ATI follow this road? That remains to be seen. µ