More information about ATI's upcoming R580 has leaked. According to several add-in-board makers the R580 will feature a socket flip chip, specifically geared for a PCI Express graphics adaptor.
But even with a dedicated socket the graphics card memory will still need to be soldered onto the board because the narrow tolerances of GPU memory don't allow a DIMM-like solution.
AGEIA might have a run for it's money if ATI has anything to say about it. One AIB commented today that the idea of a dedicated scalar mathematics processor for game physics could already be replicated on ATI's R520 series silicon, although drivers for such a project only exist in R+D departments (the vendor wouldn't let us have them, we tried). The idea of offloading math to a GPU is not a new idea; many projects exist for Linux for this already. However, the indication we had was that ATI could actually do physics calculations on the card with the graphics processing simultaneously -- the bandwidth is already there. AGEIA's physics processor has already been delayed well into Q2 next year.
More details can be read over at AnandTech. Vendors believe the ATI R580won't be available before CeBit.