Codenamed Pitcairn, the Radeon HD 7800 series board, or boards since there are two of them, will show up in February next year (2012). More precisely, Pitcairn will likely be released during the week of February 20, right after the Chinese New Year. The two cards are probably going to bear the names of Radeon HD 7850 and Radeon HD 7870.
NVIDIA will be doing something similar, so there is bound to be just as much, if not more, competition next year. After Pitcairn, AMD may launch a new dual-GPU flagship to replace the Radeon DH 6990, during CeBIT, in March.
Logic suggests the name of HD 7990, but that is still unconfirmed, just like the rest of this report of course.