Well that didn't take long. It is reported that AMD is planning to release a new 55nm RV770 based graphics card, the Radeon HD 4730. This part is basically a cut down down version of the Radeon HD 4830 with 512MB GDDR5 memory.
The Radeon HD 4730 is an attempt to ease the supply problems of the popular Radeon HD 4770.
The thing is, this card isn't based on the 40nm RV740 part but the 55nm RV770. In fact, it is a strip down version of the HD 4830 (RV770LE) codenamed RV770CE but boosted with GDDR5 memories. However, you may not be seeing mass availability as it is only available in limited quantities for certain regions whose HD 4830 stocks have ran dry.
Check out the picture.