ATI is working on the R700 which is rumoured to be a multi-core chip. FUD Zilla has some info on how this may work:
We told you before that the R600 is block architecture and that the R600 has four blocks where each had 16 Vec5 Shader units. R600 has total of 64 Shader Units divided in four blocks. The RV610 had a single block, for example with 16 Shader units, but in real life this chip has only eight. Stitching more RVC610 cores together and you will end up getting the performance of an R600.
The R600 design was not made with multi core in mind, so the Rx6x0 chips shared a memory controller and video part as well as many other features. Well, the R700 will be made out of a number of smaller chips. The single chip will represent a low end card, two chips will make up a mainstream and four to eight cores on the same die will make it a high end card.
This means that each chip will be independent, this is the way we see things now.
The R700 GPU is expected somewhere in the first half of next year.