Nvidia is preparing to launch 8GB versions of their flagship. The Gtx 980 8Gb variant will give the huge boost to sale.
Well, Gtx 980 has 4Gb of VRAM and considering single Graphics Card, 4Gb is more than enough for gaming and also more than enough for mods. But when you come to the 4k Resolution then the story is a little bit different as huge resolution requires more memory and bus width. From the AMD side R9 290X is leading in the more bus width race with 512 bits, so it has an automatic advantage over any 256 bit GPU.