Rumor has it that the bulk of AMD's Radeon HD 7000 series entry-level and mainstream cards will be rebadged Radeon HD 6000 series chips. The Radeon HD 6350, 6450, 6570 and 6670 will basically be renamed 7350, 7450, 7570 and 7670.
Moving up the ladder, the source postulates two possibilities for Radeon HD 7700 series. First, and more plausible, is that the series is based on Juniper (a hop across two previous generations!); the second is that these make use of rechristened GPUs from a slightly higher market position from the previous generation. Perhaps Barts, perhaps even highly crippled Cayman. The only real next-generation GPU is codenamed "Tahiti", but we're hearing that graphics cards based on it are said to not follow the Radeon HD 7000 series nomenclature altogether.