AMD desperately needs FinFET GPUs; their current generation consists largely of uncompetitive rebrands. Fury looks to be decent, but won't be available at the most popular price points. And AMD has nothing worthwhile for the laptop market on 28nm.
Furthermore, AMD has always been at the forefront of adopting new GPU technology; they were the first to adopt GDDR5, the first to 28nm (beating Nvidia by 3 months), and now the first to ship HBM. For this reason, I expect that they will come out with FinFET GPUs before Nvidia.
I think AMD is going to aim to bring their first GPUs on the new node to market no later than 1 year from now. If they can get them sooner, they will. I wouldn't be surprised to see them follow the strategy that Nvidia used with Maxwell, and lead off Arctic Islands with a smaller, low-end chip.