Videocardz has claimed that ZOTAC had accidentally posted a link for a new version of its GTX 1070-based Amp Extreme card - one with GDDR5X rather than the more usual GDDR5. However, this card has 8GB of this memory, as before, with the same number of CUDA cores. Then again, its TDP had increased.
https://www.notebookcheck.net/Accidental-ZOTAC-leak-hints-at-upcoming-GTX-1070-variant-with-GDDR5X-memory.375211.0.html