The SK Hynix memory catalog reveals the firm has 8Gb (1GB) GDDR6 memory chips with a frequency of 14GHz at 1.35V, and up to 12GHz at 1.25V. The site speculates the successor to the GP104 will likely end up with 8GB GDDR6, unless there's a denser memory option:
Considering NVIDIA already got GDDR5X to run at 11 Gbps, it could choose the faster option. Memory remains a cause for concern. If 8 Gb is the densest chip from SK Hynix, then the fabled "GV104" (GP104-successor), which could likely feature a 256-bit wide memory interface, will only feature up to 8 GB of memory, precluding the unlikely (and costly) option of piggy-backing chips to achieve 16 GB.