FUD Zilla reports AMD will introduce Caicos and Turks based video cards on April 19th. Caicos will be used for the Radeon HD 6450 and Turks will end up in the Radeon HD 6570 and 6670 cards. Exact details of Turks are still unknown, but Caicos will be a low-end part with a sub-$50 price tag.
The HD 6450 was already detailed and previewed and you can expect a wide variety of these cards including ones with a low profile passive cooling and various specs. We don't know the precise reason for the delay but we guess that AMD and its partners simply wanted to sync the launch of both GPUs. Of course, the date isn't carved in stone but for now the 19th of April sounds like a pretty solid info.
The Turks still haven't showed up but our current info place them on the same date as the HD 6450. Unlike Caicos, Turks is scheduled to launch in two versions, as the HD 6570, or Turks Pro, and the HD 6670, or Turks XT. The rumoured specs are pretty much in line with the OEM specs, so you can expect them both to pack 480 SPs and a 128-bit memory interface but at a different clocks for both the GPU and memory. The HD 6570 should also feature GDDR3 memory, while the faster HD 6670 will end up with the GDDR5 memory. We are quite sure that we'll see a wide variety of cards as of April 19th with different coolers, PCBs, and clocks.