Developers will optimize around what's becoming more common in the market. Last gen isn't as important as you think come this fall and next year.
4GB already has a few issues at 1440p, and you know that's gonna get worse. 1080 8GB, 1070 8GB are the new 1440p cards, and developers will see less reason to get below 4GB there. Even the lower tier cards are the 1060 6GB and 480 8GB. I'm already bracing for "High instead of Ultra" textures on many games this fall/winter.
1080P won't be that far behind in usage - it's never drastically.
We've seen this before. At launch 7850 was slower than the 1.25GB GTX 570. And the 1GB 7850 seemed pretty fine at 1050/1080 in 2012 IIRC. But certainly in 2013+ the 2GB really benefited. I can attest with using more than 1GB at times on my GTX 460 equivalent which is a much slower card.
Why did this happen? Because all the top 4 GPUs in 2012 for each company were 2-3GB minimum. So developers saw less and less need for keeping VRAM below 1GB, or even 1.5GB (570-580 started to feel the pain too). And the Top 4 Nvidia GPUs are 6-12GB, and the top 2 AMD Gpus (which are equal to the 4th and likely 5th for Nvidia) also have 8GB options available. As the 980 and 970 ownership starts to fade away a bit, there will be less desire for <4GB textures on Ultra 1080p. Not the biggest deal to run a texture setting lower, but something to consider.
1060 6GB should be fine for quite some time though, although if you hold onto it long enough the day will come that 1080p textures will require more than 6GB, but you'd probably have the other settings at Medium or something and would want to upgrade by that point anyway.
That's why as I posted earlier I find the choices for $150-$250 (MSRP anyway) to be rather fascinating with VRAM considerations. If your max was $200, what would you take? Honestly, I'd recommend either going under budget for the 470 4GB and upgrading sooner with the savings, or going 1060 / 480 8GB (depending on preferences) and riding it out longer.
We still need 470 and 1060 3GB (1050?) benchies, but I anticipate that being my recommendation. $150/$250, and round up or down if your budget is in between. Looking forward to 1050 and 470 reviews to see how things are looking.