GK110 is another gpu from nivida that's made on 28nm and has a big core die. That's all that's know. Some ppl say that the manufacturing such a big die on 28nm is so bad we might only see GK110 in limited numbers as a Tesla card and not a consumer gpu.
There is no suggesting that this was the real 680 GTX because it's rumoured to be out in 2013.
With Nvidia, when there's a 110, there's also an earlier castrated 100. They use the nomenclature of 100-109 for their tick, and then 110-119 for their tock of the same architecture.
The GK110 is the tock of Nvidias 28 nm Keller range, the GTX 680 was originally planned as the tick of this GPU, but they have now scrapped the high end tock card for many reasons:
GK104, originally GTX 670 Ti beat the 7970.
The GK100 tick card wouldn't have been ready for several more months.
Naming the GK104 as GTX 670 ti would leave a lot of customers waiting for GTX 680 and not purchasing GK104
GK104 is significantly more profitable at its current price point than the GK100 tick would have been.
Abandoning the high end tick card now gives Nvidia more time and resources to put into developing the GK110 tock. This card was originally due for early 2013, but the latest information on Nvidias timelines now show it as planned for Q4 2012.