AMD's upcoming HD7000 Series (Southern Islands) GPU details have been leaked through Catalyst 11.7. We already detailed AMD's next generation Graphics Architecture here which would be used inside the upcoming 7000 series cards.
According to the chart, AMD is looking forward to release a new Dual Chip based card based on the NewZealand Core named HD 7990 which would be its next Flagship card. Single chip based High end GPU's would consist of Tahiti XT based HD7970 and Tahiti Pro based HD7950 which are replacements for the Antilles based HD6970/6950 graphics cards.
Thames XT (HD7870) and Thames Pro (HD7850) as the name suggest would replace the Barts based HD 6850/6870. Thames LE (HD 7790) would be a replacement for the Barts LE based 6790 Mid-End card. Lower end models to replace the Turks based HD6670/6650 consist of HD7670/HD 7570 based on Lombok Core. You can check out the chart below for more details:
Clock and GPU models would be detailed in a few months since AMD is planning to release the cards by Q4 2011. Nvidia has also started working on its Kepler based GPU's and is also aiming for a Q4 2011 release.