GDDR4 is just ready and next year we can already expect GDDR5 memory:
DRAMeXchange indicates the raise in working frequency in GPU is the main force to push the development on GDDR memory, providing a higher memory frequency to fulfill the need of bandwidth. Samsung and Hynix have already give GDDR4 samples to ATi and nVidia. The first GDDR4 graphic card is available in August as ATi Radeon X1950XTX, using Samsung K4U52324QE-BC09 (16Mx32, 1.8V, 8K/32ms, 0.91ns @ 1100MHz). The release indicates the move to GDDR4 era. Not too long to wait, manufacturers plan to make GDDR5 available in late 2007. GDDR5 is now in design stage and first sample would be sent to partners in mid-2007.