I reckon AMD will launch the Radeon HD 7990 once they know exactly how fast Nvidia's most high-end card is.
Today, on January 31st, AMD is going to launch HD 7950, the second graphics card from HD 7000 series. This GPU has fewer stream processors, and somewhat lower core and memory clock speeds compared to previously released HD 7970. The HD 7950 should also be cheaper than the 7970. A number of more affordable HD 7xx0 cards will be coming later in the first quarter of this year. MSI yesterday published HD 7900 series infokit, that includes launch dates of AMD HD 77x0 cards, and launch month for HD 78x0.
According to the roadmap, HD7750 and HD7770 will be available on February 15. Both cards will have 1 GB of GDDR5 memory, and from previous reports we also know that the boards will have 900 MHz core frequency, 896 and 832 stream processors, and 56 and 52 texture units. The HD 7770 will be priced at $149, and HD 7750 will be $10 cheaper.
In March AMD will release HD 7850 and HD 7870 GPUs, both featuring 2 GB of RAM. The 78x0 series will have core and memory frequencies, comparable to 77x0 series, however they will pack from 1280 (HD 7850) to 1408 (HD 7870) stream processors, and from 80 to 88 texture units. HD7870 will retail for $299, and HD7850 will be $249.
The roadmap doesn't have launch date for HD 7990 card. Based on older reports, this dual-GPU card may launch in March 2012, and it will cost $849.