True
You can expect 5% more efficient shaders. At the best 10%, not more. This efficiency comes from the architectural changes but not from the die shrink.
Doing some math based on the picture:
980 = 2,6 points of performance
1080 = 4,4 points of performance
So we can expect 1,7 times more performance.
Efficiency:
980 = 165W
1080 = 180W
1,1 times more power draw, that means 1,54 more power efficiency considering that it is 1,7 times faster.
Shaders:
980 = 2560 CUDA cores, 1607MHz
1080 = 2048 CUDA cores, 1126MHz
So the 1080 has 1,25 times more CUDA cores and 1,43 times higher frequency. That means that the 1080 should have 1,79 times higher performance over 980. If to take the architectural efficiency increase in account then it should be over 1,79. If the architecture improved 5%, it should be around 1,88 times faster.
But yeah, look back to the image and you can see that NVidia shows that it is 1,7 times faster. 1,7 is less than the expected 1,88.
The 1080 might be disappointing, I think it has some flaws and bottlenecks. One of those bottlenecks must be the GDDR5X memory. No HBM means bad news.
Meanwhile AMD has smaller dies and GDDR5. Those GPU-s will be cheaper to produce. I think that AMD made a good move with the shader performance and memory bandwidth configuration. They didn't push too far and their cards seem to be more balanced. They also launch Vega in october with HBM2 for the richer gamers.