Although this was a rumor for a long time now we now know that AMD skips 20nm and jumps onto a 14nm fabrication node for their 2016 GPUs. Yields in the 20nm have been a massive failure and as such many manufacturers are skipping that 20nm node.
The AMD Radeon 2016 line-up tagged under code-name Arctic islands as such will jump straight towards 14nm FinFET technology with stacked graphics memory dubbed HBM. as expreview reports. A huge jump considering the current products are still at 28nm. What this means is a smaller die and lower voltages. E.g. a Hawaii GPU would be precisely half the size of what it currently is.
Currently Intel and Samsung are the only nodes that can offer 14 nm production, so it will be interesting to see where the wafers will be baked. For example, Intel is manufacturing "Broadwell" CPUs on 14nm and Samsung is manufacturing the Exynos 7 SoCs on 14nm.
It will be interesting to see how the lineup of 2015 shapes up to be, but expect 28nm parts.
AMD Greenland will be the R9 400 Series Flagship in 2016.
From that new lineup, the Greenland GPU would be AMD’s first GPU to be built on the 14nm likely fabbed by Gloablfoundries. It would be the flagship GPU dubbed the R9 400 series which will be tied to second generation High Bandwidth Memory (stacked memory).