Interesting news from TPU today, they noticed via Donim haber that dual-GPU based Radeon HD 7970 X2 cards from board parters might be in the works. That means that the board partners are working on their own dual-GPU solutions based on Tahiti GPUs. 

AMD is expected to release a RadeoN HD 7990, but that one seems to be delayed.Initially we expected that one to be released during Computex 2012, but so far nothing substantial has surfaced. DonanimHaber now reports that manufacturers are tired of waiting for actual Radeon HD 7990 model from AMD, so they will come up with something new.

The specs on these things can go all directions, it would make sense though for two 28 nm "Tahiti" GPUs to be used with even higher clock frequencies to they'll be able to take on the GeForce GTX 690.

As stated, it's all unconfirmed, but yeah .. that would be an interesting development.