Right now the 14nm process is for CPU's most of which have iGPU's. The next die shrink for GPU's 14nm or 16nm for the 2016 lineup, well for AMD, nVidia will probably do the same, along with HBM2.
Reason it's behind is mostly because Intel has so much money for process research, however they were recently beat to a functioning 10nm process, but it will take time for it to mature enough for market introduction. That's is why Broadwell was delayed, the 14nm process yields were problematic.