It could very well be that AMD is working on a Dual-GPU 7970 GHz, thus Radeon HD 7990 edition graphics card. Rumors are that this is being developed under codename Malta. Both GPU's would be clocked 'well' over 1 GHz. But there's more ...
According to Fudzilla, AMD is preparing at least two new graphics cards. One would be Radeon HD 7790, with a new GPU called Bonaire XT. This would be a mid-range segment product with performance close to the HD 7870. Apparently AMD will not allow its partners to factory overclock the cards based on this GPU though. There is no specific release date given, but the product is believed to arrive in first half of this year, probably in April.
And then there's the AMD Radeon HD 7990 (Malta) - AMD would be prepping this product to anticipate and the GeForce GTX Titan and sure, the GeForce GTX 690.
With two Tahiti GPUs likely XT2 this a dual-gpu card could haul serious ass alright. Still it is based on a speculation from a source that has been wrong on many occasions. You may assume however that the card would offer a GPU core clock above one GHz, and that would seriously interfere with NVIDIA’s flagship products.