Word is going around that NVIDIA is preparing to launch a new GeForce GTX 1060 3GB variant that will be based on the GP104-140 GPU. These cards will not be faster than the current GTX 1060 models and will likely have a poorer power efficiency.
It's really an old tactic being used here, the main reason for the new SKU is because NVIDIA is sitting on a lot of GP104 chips that did not make the cut to be sold as a GTX 1070 or GTX 1080. This means these parts don't have 1920 working CUDA cores, so instead of letting them go to waste NVIDIA will be selling these chips as GTX 1060 parts.
Those cards will most likely have higher power requirements than normal GP106-based GTX 1060’s. For such reason, to avoid any ambiguity with power-efficiency claims they will not be advertised worldwide. From what’ve heard those cards could be China-exclusive.
So to be clear, this is not a rumor, we just don’t know all the details yet. In fact, there’s even a new entry in the latest driver, revealing the ID of this card (1B8_ family means GP104):