Qimonda recently achieved 1GHz GDDR3 memory and is now aiming for 1.2GHz. They aren't really working on GDDR4, they rather want to switch to GDDR5 later in the year.
However, we weren't able to dig out more details about GDDR5 spec, even after calling the father of both GDDR3 and GDDR4 specs. But never mind that – it is more than obvious that Qimonda now targets massive volumes, and if everything goes the way Qimonda is planning, GDDR3 memory chips from Xbox 360 (700 MHz clock, 1.4 GHz effective) will offer such pricing that graphics manufacturers should jump the gun and offer GDDR3 memory tech even with lowest-end products.
Recommended: Click here to Update all your outdated drivers