You think they'd sell well at that price? What made the 970 such a success was the $330 price tag. If that was $400 I doubt they would have sold anywhere near as many, but at $330 they were able to shift the new normal up from the $250 they were getting when everyone bought GTX 760s. Putting 70 series at a price low enough to get mass adoption while making a really lame 60 series card made them a boatload of money this generation while putting a ton of pressure on AMD, why stop a winning formula?
NV realized there were still a lot of HD4000-7000 series hold outs that didn't upgrade to 285/280X/290/290X and capitalized on the opportunity to get AMD users to switch. Now that these gamers are in the NV eco-system with a 970, unless Polaris can compete on performance (doubtful given the rumors of it bringing 970/290X performance to lower tiers -- i.e. That's not an upgrade path for 970 users), NV can easily raise the price to $399-429 and get the same customers to upgrade for 50%+ boost over the 970. If I have a 970 now and 1070 is 50% faster for $399-429, I am not waiting until December 2016/January 2017 for Vega. AMD released their road-map so NV knows this.
Another possibility of course is the return of 3-tier mid-range cards:
680 -> 1080
670 -> 1070
660Ti -> 1060Ti
If Pascal is 2X perf/watt, 1060Ti alone could ~ 390X/Fury. Then this could be a $299-329 card.
It's also possible that the performance gap between 1070 and 1080 could grow to 20-25%. We have seen a larger separation between 970 and 980 as opposed to 670 and 680.
Either way, unless Polaris can beat Fury X by 20-25%, I don't see it competing with GP104 and that means way less pricing pressure on NV in 2016. On the performance/watt, Nano is still a good card. Since AMD has way less $$$ than NV, I wouldn't doubt it if the Nano/Fury/Fury X got big price cuts (aka 290/290X did when Maxwell launched) to stay relevant until Vega. I think instead AMD will do something crazy like Polaris "390 performance" for $199-229 and "390X performance" for $249-269. This allows AMD to regain a ton of market share on the low end while using Fury/Nano/Fury X as $349-399 mid-range. 1080 then should have the market all to itself for most of 2016. Unfortunately that is how I see it given everything coming out from AMD's rumormill is small die/low power/mobile-laptop focus. I am of course speculating but why didn't AMD show us Polaris 10 against GTX980?
Besides, an after-market 980Ti has nearly 2X the perf/watt of a 290X at 1440p:
100% vs. 53%
http://www.techpowerup.com/mobile/reviews/Gigabyte/GTX_980_Ti_XtremeGaming/24.html
That means even if Polaris has 2.5X the perf/watt of 290X, GP104 will slaugher it. It's my quick math based on what both firms have said about next gen perf/watt and where their 2013-2015 cards sit wet to each other. AMD needs to get 2.5X the perf/watt from Fury X to actually get to Pascal's 2X over Maxwell given how far behind they are right now.
^ This is why AMD is showing Vega improving perf/watt again over Polaris -- because 2.5X over GCN 1.0/1.1 isn't good enough to match Pascal's 2X over Maxwell. Notice how AMD kept focusing on bringing VR GPU spec to the masses? That literally smells like HD4850/4870 strategy of bringing Polaris price/performance and low power. Remember, Pitcairn, at least for the first 2 years of its life, was not a GTX670/680 competitor. That's why I just do not see Polaris 10/11 competing against 1070/1080, maybe against 1060/1060Ti.
Another way of looking at it is we have a leak of 2304 shader 256-bit Polaris card. Even if we assume the same 35% increase in IPC AMD could get on Stream Processor that NV managed with Kepler --> Maxwell, then bump GPU clocks 30%, that means 2304 Polaris under these conditions is only as good as a ~ "4044 shader" Fury X. Even with only 50% perf/watt over 970, 1070 alone would already beat such a mythical Polaris 10 card. 1300-1350mhz GPU clocks and 35% per Shader core IPC increase are some wildly optimistic assumptions I just made for Polaris. I think it won't be anywhere close to that!
This is why I am pessimistic on AMD in 2016 as far as the desktop $349+ market segments go.