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There are rumors that AMD will launch their Radeon HD 9000 series cards in about 2-3 months. Yes, 9000, not 8000; the 8000 series is OEM-only rebrands of 7000 series parts. 20 nm isn't ready yet and seems to be coming slowly, which means that the cards will still be on 28 nm. The existing Bonaire card, the Radeon HD 7790, would likely get rebranded into the 9000 series.
I'd expect the lineup to include the old 7790, a cut down version of it, and a more efficient big GPU chip that can compete with the 7900 series (since the Tahiti chip is a power hog). AMD may or may not have a high end chip to compete with Nvidia's GeForce GTX Titan and GTX 780. There's also a decent chance that AMD will launch a new low end chip to replace the old Radeon HD 6670; Sapphire is rumored to launch a 384-shader Radeon HD 7730 soon.
Really, though, this is bad news, as it looks like the 20 nm cards that would be the real advance aren't coming anytime soon. You don't launch new 28 nm cards and then move to 20 nm three months later; if you were going to do that, you'd skip the new 28 nm cards. All of the foundries seem to be struggling with 20 nm, though TSMC is promising a 16 nm FinFET process node only a year after 20 nm, while Global Foundries says that they'll have their 14 nm XM node only a year after 20 nm. Of course, those dates could easily get pushed back as they get nearer.
Years ago, everyone seemed to agree that getting to 22 nm or so was doable, but the question was about beyond that. While it's still coming, the "beyond that" seems to be troublesome for everyone. Or at least for logic chips; there is already 19 and 20 nm NAND flash widely used in many products.