Now BenchLife delivers word that there is indeed a 3GB GDDR5 version of the GeForce GTX 1060 - but apparently this model has fewer CUDA cores.
If the information is correct, the GP106-400 is the one with 6GB GDDR5 while the GP106-300 has 3GB GDDR5. The latter reportedly has 128 fewer CUDA cores than the 6GB model, resulting in a total of 1152 CUDA cores.
Via: VideoCardz