New details about the NVIDIA G72 and G73 were released. It looks like these two GPUs will be pin compatible with the NV40 and NV43. This means they may have the same PCB as the 6600GT, but with a different GPU. This will lower the cost for the manufacturers as they don't need to design new boards.
It also means G72 and G73 will launch very fast when the decision comes from NVIDIA as vendors can very easily switch production from the older chips to the new ones. Two vendors confirmed with us that they are already retooling their PCB for six pin 12V molex with the anticipation that G72 and G73 SLI might need the additional power, but even NVIDIA won't comment to the manufacturers at this point.
There are also talks NVIDIA has bigger plans, like flip chip GPU sockets for motherboards.
Apparently, inside NVIDIA engineering teams have several prototypes where the GPU, rather than the CPU, is the main focus of a motherboard with two sockets: one for the GPU and another for the CPU. Whether or not such a machine will ever see the light of day is difficult to say right now. However, the idea of pin compatible GPUs already suggests that we are halfway there when it comes to buying GPUs the same way we buy CPUs: in flip chips.