unknownofprob :
Only reasoning people have come to understand that Vram is more beneficial is by user reports, along with all the game recommendations that people believe the "GTX 660 3GB, 7870 3GB and GTX 760 4GB" are actually needed.
These are your examples, not mine. I am no way using this to support my argument. Users will make many unfounded claims, and you will see plenty of this on these forums.
unknownofprob :
Without a doubt later on (not in the next 2 years) these 4GB cards will come in handy, especially when 4k gaming becomes mainstream, but as for now goes, there isn't much logical and documented fact to do so. By the time you mention supposedly comes when these card will shine, they will already be outdated, and not sufficient enough but that isn't due to it's Vram amount.
I am writing purely of 1920 x 1080 resolution.
My personal experience is that with HD texture mods and anti-aliasing enabled, Skyrim will exceed the 2 GB of VRAM on my card and suffer severe frame rate drops entering areas where new textures must be loaded. I can see the peak in VRAM corresponding to the drop and reducing the size of textures or anti-aliasing resolves the issue. In this resolved state I can see VRAM usage approaching but not reaching the 2 GB ceiling.
I base the Watch Dogs figure on a guide published by Nvidia for suggested game settings on their own cards:
http://www.geforce.com/whats-new/guides/watch-dogs-graphics-performance-and-tweaking-guide#textures
Based on these I state that 3 GB of VRAM is required today to run the highest available settings at 1920 x 1080 resolution in some games.
unknownofprob :
With your lovely examples of what you listed about the economy, you missed one crucial thing and that is this -
The near future isn't expected to have double the capacity in a matter of 2 years, but a faster increase then normal over a longer period of time (and that time is 2 years).
These examples show planning for the useful life of the product or infrastructure. The time scales and rate of increase vary of course.
The high end cards being released 8 years ago had 768 MB of VRAM, so a required amount of 512 MB doesn't seem unreasonable.
Lets say that the 2 GB requirement for highest settings was reached two years ago with the release of Far Cry 3.
That is a multiple of x4 in 6 years, which means doubling every three years.
If this trend continues you would need 6 GB of VRAM in three years from now for the highest settings. This seems pretty reasonable to me.
It would be fair to say that in three years time these cards won't be fast enough to run the highest settings anyway, but the trend also suggests the VRAM requirements for the highest settings will reach 4 GB by the end of next year (3 years from the release of Far Cry 3). This to me makes 4 GB of VRAM a minimum for these high end cards, and Nvidia seems to have picked the same number.
I'm glad to have a discussion with you about this. There are a lot of ill-informed statements on the forums and if you can bring reasoning to some of those threads it may help someone. I'll be even happier if I convince you that buying a card with 3 GB of VRAM today and expecting it to run the highest game settings for the next two years is unlikely because this could save someone else disappointment.