Even though the ATI R600 class GPUs are not yet on the market, there is already some talk of the ATI R700 successor to the ATI R600. It seems that perhaps in the R700 ATI will use multiple small GPUs on one graphics card rather than one large GPU for all tasks.

This would be like using a multiple CPU system for your computer vs a single CPU solution. I would assume you would be able to have one GPU handle physics, one handle shaders etc if you wanted. On the other hand, just make a whopping load of unified shaders to handle everything you might need.
Who knows if this bit of info the guys over at The Inq dug up is accurate, but it would make for some interesting graphics cards if it were correct. Cooler, draw less power because you could possibly turn off GPUs not needed at any one time.