An 1070 has 1920 cores so 2048 cores is not much of an upgrade. The 1080/1080Ti has 2560/3584 cores for comparison.
The only point I can see is if its built with 14nm technology like the 1030/1050/1050Ti while the rest of the 1000-series cards are based on 16nm fabrication. I'm not sure that slight efficiency upgrade would worth it to push a new card but who knows.
i think they are making them strickly to destroy any small chance Vega 56 had a beating the 1070/1080 ;p
They have been confirmed now by Gigabyte (inna terrible "IT" reference"), to be dropping around Halloween
I may grab one for the hell of it, it will be a Miners card for sure with G5 mem, and guaranteed it could NEVER be as bad of flop as vega atleast ;p