Seems the rumor mill may have gotten it wrong.
There never was and there never will be such a card.
There is no financial sense to release a slightly updated 55nm chip with a bit better specification to counter Nvidia, and as we said before, the next chip from ATI is 40nm and this should happen in Q2 2009 time. GT200 55nm chip and the new GTX 260 with 216 stream processors and a 180 driver are enough to put a lot of pressure on Radeon HD 48x0 sales, but ATI can now initiate price wars that should help the company get by until the new chip arrives.
AMD might have one more mainstream chip coming in Q1 2009 but we can assure you that there is no RV775 or any kind of faster RV770 card that will launch shortly. The next performance card from ATI is 40nm and that's it