Are you freakin kidding me? Are you playing on a 27" 1440p monitor in your sig? If so you'd just be wasting your money for more VRAM. I can guarantee you that. I play at 1600p and I'm fine with 2gig vram. I never exceeded my vram, even if I did, I couldn't tell.
I have exceeded 2GB VRAM on my 1440P. But ya, you certainly would not need more than 4GB, even for surround. Since 3GB might be cutting it for really demanding surround setups and the next step was 6GB, I'm glad NVIDIA went that route. I have exceeded 3GB before on my multi-screen setups with my 7970's.