First answer from AMD:



2nd generation PCI Express bridge design of course means that PLX chip has been upgraded to support PCI Express 2.0 standard.

"Next generation GPU inverconnect for improved scaling" means more bandwidth for data transfers both between cards and between system memory.

The bandwidth between both GPUs has been bumped from 6 GB/s to 20 GB/s (According to to HardOCP preview).

Waiting for more information