TechPowerUp found two photographs of a stripped AMD Radeon HD 6970 graphics card. The pictures reveal the card uses 8+6 pin power connectors and features a 6+2+1+1 phase digital PWM voltage regulation design. Additionally, the reverse side of the PCB has no memory chips, which implies AMD might be using 2Gbit memory chips to get 2GB GDDR5 on the card.
The size of the die, and taken that Cayman is a 40 nm GPU, indicate that Cayman is not much bigger than Cypress, it should be about 400~500 million transistors higher compared to Cypress.
Given the roughly 2500 million transistor count, the stream core count of 1536 seems more realistic. AMD is said to be using an architecturally superior VLIW4 stream processor design that increases performance per mm² die area.