It was rumored already that AMD is about to release a R9 285 based on the new Tonga GPU. Tonga will likely have the very rather similar shader processor count as one of the "Tahiti" GPUs yet will have higher clocks and a 256-bit wide GDDR5 memory interface. These cards will get 2GB of graphics memory 2 GB of memory. 

The Tonga graphics architecture will be built on the 28nm node from Global Foundries and would feature a new design scheme introducing latest architectural improvements such as new ACE (Asynchronous Compute Engine) Units and more focus towards compute shaders. The main focus of the Tonga GPU is said to be the power efficiency. 

Tonga will keep the basic technologies of the Radeon lineup such as Mantle, TrueAudio and XDMA for CrossFire support. Little is officially known about long rumored Tonga, but the GPU should be locked and loaded with a 256bit interface that they should have 32 CUs and 2048 Shader processors. Next to that it should get 32 ROPs and 128 Texture memory units. 

Several AMD Radeon R9 285 Tonga based GPU cards Spotted