The alleged GTX 1070 Ti was originally spotted as a part of a specifications list on My Drivers site, caught by PCPer.com, and is listed as the Asus GTX 1070 Ti Strix O8G. While there were no precise details regarding the card, the O8G in the name suggests it packs 8GB of memory.
Further rumors suggest that it could be based on the latest GP104 GPU and pack 2304 CUDA cores, which would put it smack between the GTX 1070, which comes with 1920 CUDA cores, and the GTX 1080 with 2560 CUDA cores.
Since Nvidia has already launched GTX 1080 with 11Gbps GDDR5X memory, the gap between the GTX 1070 and GTX 1080 has become significantly wider.
In any case, this will put a lot of pressure on AMD's RX Vega lineup and could give NVidia a significant lead in the market. In the end, it will all come down to the price/performance factor, availability and the MSRP, which tends to suffer from a big demand from coin miners.