Consoles are the speed limit, and with 8GB shared memory and 5GB available to game developers, how much of that is going to be graphics? 4GB at MOST. More likely 3GB or less. Gamedevs aren't going to program for cards that very few people own, that's just a fact and it's always been that way since Crysis and Crytek throwing a fit over how few sales they got vs how many they expected to get.
The only way you are going to need more than 4GB anytime soon is if you run tri-screen 4K with anti-aliasing turned up, but only a fool would do that since pixel density on 4K screens is so high that AA is largely or entirely superfluous.
I would go far as to say that 4GB VRAM will last from now all the way to the next console generation for single-screen 4K or lower. Furthermore, in 3-4 years the people who can afford crossfire halo cards and tri-screen 4K can simply upgrade their cards in a few years if 4GB is not enough. There is no point in trying to "futureproof" by buying 6GB+ VRAM cards for games. For pro graphics or Tesla, sure. Games? Pffft. Re-upgrade down the line if you have to.
P.S. It remains to be seen if DX12 rumors are true about how you can use both banks of memory in Crossfire under DX12 instead of mirroring them. If that's true then that's makes it even less necessary for >4GB VRAM.
You can't really say that.
Also, consoles run 1080 best case scenario and many games are less than that. There are many variables such as dx12. It may get rid of much of the windows overhead but we don't much at all about it. Just as an example, mantle didn't do so well on 2gb tonga.
If consoles are struggling with 1080 and below, PC ports could come with higher textures. The bar could really be raised with dx12, there is no way to predict the future.
I am not saying that 4gb will be an issue any time soon. I absolutely hope not cause I have a 4gb card. But if it does, we just deal with it like we always have and move on.
Personally I think 4gb will be fine for a good while. But we can't predict anything with so many industry shifts coming, we truly are heading into the unknown. But I do find it strange that some people are insisting that 3.5gb is so bad and a huge problem, they say 12gb is just a total waste and worthless, but 4gb is just perfect for yrs and yrs to come. I mean, if 4gb is great for the 290. It 3.5gb is condemning the 970...how can these people insist that a card with a suggested 50% increase in performance be perfectly fine with 4gb as well? I am not saying it won't be, just that it doesn't seem like sound logic.
I think that we can't make any such assumptions with so many unknowns. We can't say that 12gb is just a total utter waste for the gm200, just pointless but then turn around and say 4gb is perfectly fine for a card 50% faster than the 290x. How can we make any claims at this point at all. It may very well turn out to be just that case. The 12gb gm200 may be completely worthless but we must wait and see.
These are areas we know little of. We don't know how the gm200 will fair with all that ram and we don't know the first thing about HBM on a graphics card.
HBM may offer more than imagined. 4gb HBM may stomp all over 12gb gddr5.
Its just unknown. Really, al we have to do is keep the cores saturated at all times. We don't know which route images be the drawback or any of the pros and cons when it comes to performance. And that is today, the ramifications right now and there is no way we can have any clue as to what they will be the future