Take a gander at this picture below as possible proof of the existence of an unreleased GTX 1070 Ti.
The picture comes from My Drivers, who also posted untranslated commentary about the card here. The text describes a card with 2304 CUDA cores, falling between the GTX 1080's 2560 and the 1920 present in the GTX 1070. We do not have any insight into the memory clock on the card, nor if it is GDDR5 or GDDR5x but it should also fall between the two existing cards.
That's all the info we have for now on this card, hopefully we can find one before the miners do as this card is likely to be very popular with that segment.