Did you miss the release of 3 Polaris cards this summer?
Next AMD graphics release isn't scheduled until after Christmas. Should be Vega - high end chip with HBM2 memory. Don't know much else about it. Watch this space...
EDIT: and just a quick thought - whilst nvidia may be going with asymmetric memory channels on this, the manifest may also be incorrect about the bus width - a 320 bit bus would give you a lovely symmetric arrangement of 10GB GDDR5X and be a differentiating point to both the 1080 and the Titan X...