The guys from Hexus saw a working dual Radeon X1950 Pro from Sapphire at CES 2007:
Laid bare and next to a not-so-small Sony Ericsson K800i for reference, the dual-GPU board packs in a couple of Radeon X1950 Pro GPUs clocked in at a reference 580/1400 for GPU and RAM, respectively. Hooking them together is a bridge chip that you see just below the left-hand GPU. The card is equipped with a 1024MiB framebuffer, equally split over both GPUs. The PCB is also taller than normal, although enthusiasts considering this kind of SKU should have adequate room in their chassis.
Power requirements dictate that, like NVIDIA's GeForce 8800 GTX, two PEG connectors are required to supply the juice when the card is put under maximum 3D load. Also, note the CrossFire connectors on the top-left of the card; Sapphire's looking towards a quad-GPU setup that, effectively, is CrossFired twice. We'll have to wait until supporting drivers are available, though.
Check it out at Hexus. The card will be launched in February.