TPU picked up a German rumor that AMD is planning to introduce some 28nm GPUs in the second week of December. It's expected that these chips will be low-end to mid-range chips, and not high-end parts.
One of these sources specifically named December 06. Details on whether the launched GPU will be for the mobile (notebook) or desktop (graphics card) platforms; or even whether it will use the VLIW4 or so-called 'NextGen' compute architecture, are not known at this point.
Another source reinforced the theory that the launch will be more about symbolism than volume manufacturing for sales. It's likely that a small number of these GPUs will be manufactured, just about enough to send to OEMs for their qualification, and perhaps even the media for published performance testing.