WCCFTech's sources inform that the GTX 1060 successor should feature 8 GB GDDR6 VRAM and will be launched in late September for around US$500, while the GTX 1070 successor would also get 8 GB VRAM, but will be launched in mid-September for US$600. As for the flagships, these are said to feature 11 GB GDDR6 and would launch in early September for US$700.
https://www.notebookcheck.net/NVIDIA-s-next-gen-GTX-GPU-wattage-memory-and-pricing-details-sent-to-AIB-partners.318558.0.html