Looking at the GTX 1070 and 1080 and the Radeon R9 390, I see game developers programming their games for 8 GB VRAM. I've heard that the GTX 1060 will be launched with 6 GB VRAM, so that would be a sub-optimal choice. But could manufacturers release GTX 1060 cards with 12 GB VRAM? Or are there intrinsic limitations which prevent this? Similarly, someone with a 21:9 5kx2k display might benefit from more than 8 GB VRAM so is there anything to prevent a 16 GB GTX 1080?