Agreed. A 3gb card will struggle with some games right now, let alone 1 year from now. If the GTX 1060 6gb is $249 and is within 2-3% of GTX 980, it will be an even trade off (dare I say I better one), to get 8-10% more performance and a lower TDP vs. 2 more gb of vram. These are 1080p cards despite AMD hyping up 1440p and 6gb should be plenty for the next 2 years at 1080p. Plus the 1060 will surely have more OC headroom than the RX 480, which seems to have adopted undervolting as a positive feature instead of overclocking.
Just note when the 1060 is in retail, it's competitor isn't the crappy reference RX 480 that's running overvolted and throttling.
Both my RX 480 with an undervolt runs cooler/quieter, less power, while being around 4% faster than stock settings. Not a big perf gain, but now it's around 390X/980 instead of behind and the perf/w obviously go up. It even runs under-volted with a small OC so there's room there for AIBs to tweak it better than AMD's effort.
Custom RX 480 should be better than reference, so these cards are the true competitor for the 1060.
It's going to come down to ~ same price & performance, 1060 wins on perf/w, but rx 480 wins with 4GB & 8GB vs 3/6GB.
It's not great for AMD, but it will be an interesting battle in the mainstream for sure.