According to Chinese tech site Inpai, a new, beefed-up HD 5670 is in the works. This new mainstream card could perhaps be in anticipation to the lower-priced Fermi parts that are expected to arrive sometime after the summer (perhaps September).
The supposedly new HD 5670 gets a big stream processor boost, going from 400, to 640. This is a pretty huge boost -- we'd almost expect AMD to rename this part the HD 5730, or something, to differentiate the old and new cards. In fact, it seems this new HD 5670 will use the Juniper GPU that powers the HD 5750/ HD 5770 -- just with some of the shaders turned off. This new card could be a efficient method of utilizing spare Juniper GPUs that AMD has around (perhaps ones that could not make the grade to be HD 5750's.)
While the new HD 5670 is getting the huge shader boost, the clock speeds are staying the same apparently, with a the core remaining at 700MHz, while the memory clock holds steady at 4000MHz (effective).
There has been little info on this video card in the Western hemisphere, so for now, this product seems likely to see only a Far East release. However, it may indicate what AMD may have planned to release when the Fall comes and there is more competition in the $100-$200 price point.
Card labeled as Sapphire HD5670 512MB Platinum Edition