According to reliable sources on the Tweaktown site, the Radeon RX 680 graphics card will be powered by the new Navi GPU and will have 8GB of GDDR6 memory, with performance between a GTX 1080 and GTX 1080 Ti.
RX 680 would have a performance between the GTX 1080 and GTX 1080 Ti
We know that the next step for AMD and its Radeon graphics cards will be the launch of the Navi-based GPUs, which will arrive next year. Rumors are already beginning to spread about the RX 680, which should have a price in the range of 299-399 dollars, in a fierce fight against the GTX 1080 Ti, especially with a faster GDDR6 memory. The RX 680 card would use the Navi 10 chip.
After the release of Navi (and derivatives) AMD would counterattack with Navi 20 at 7nm as a high-end GPU in the 2020-2021 periods, but in the meantime it would have to make do with a really good mid-range graphics card that is placed below $400 (or well below) to do damage to Nvidia, which should already have the Turing graphics cards at that time.
Navi 10 at 7nm would allow AMD to approach the Nvidia variants but at a lower cost thanks to the use of GDDR6 memory instead of HBM2. On the Nvidia side, GTX 11 is already on the horizon and you can already hear possible names, GTX 1160 or GTX 1165, and with graphics cards that will lead the performance, GTX 1185 or GTX 1190, two names that are handled according to the sources.
The picture seems to complex for AMD in the graphics card industry, quite the opposite with the CPU market, where they fight as equals with Intel.