There are two ways to quad sli
1. 4 pci-e cards in 4 pci-e slots (4 cards with one core each)
2. 2 7950's in 2 pci-e slots (2 cards with 2 cores each)
No 2. is the way that most system makers are doing it BUT it isn't available for retail purchase (just the cards I mean).
If you look at the picture of the 7950 on nvidia's site there is no place for an sli connector to go, on the other hand the pictures of them on sli zone show each board with a connector. I think that is the difference between what the system builders get and what's available retail.
On the other hand, i heard that nvidia is going to make sli possible without the bridge and run by the chipset, so with a new driver release you may see the retail 7950's able to run in sli without the sli bridge.