VideoCardz wraps up some fresh rumors about AMD's next-gen Big Navi GPU. First up, there's a rumor that one variant of "Sienna Cichlid" features a 2048-bit memory bus, which implies it will use two HBM stacks. If correct, this is unlikely to be a part for the consumer market.
A 2048-bit memory bus would indicate that the GPU features two HBM stacks (each requiring 1024-bit bus). This opens a possibility for a 2×8 GB or 2×16 GB (Samsung Flashbolt HBM2e) stack configuration.
Next, there's a rumor that Big Navi will feature a 512-bit memory bus with 16GB GDDR6 memory:
The user did however reveal that his sources are confident that the card features 16 GB memory. He later added that it should be 512-bit GDDR6 memory, which does not correlate with the first rumor. This would suggest that the card has GDDR6 memory instead (and honestly as everyone expected).
It's also said that final specifications aren't known yet as AMD hasn't send out finished PCB yet.