Once again I have an exclusive story that AMD will have Navi ready to go sometime in July-August 2018, with a Navi-based professional card being launched at SIGGRAPH 2018. We're still waiting for AMD to launch Radeon Pro SSG, something they unveiled during SIGGRAPH 2017 that hasn't yet materialized. In the meantime, Radeon Technologies Group boss Raja Koduri has taken a sabbatical from the company until early-2018.Not a lot is known about Navi, the only thing AMD shared so far is that it will be made on a 7nm process and that it will use a next-gen memory technology.
It's also believed that Navi could be a modular chip, as AMD is expected to move away from big monolithic GPUs in favor of smaller dies that are linked via Infinity Fabric. NVIDIA has also expressed interest in this, but AMD seems to be a bit ahead in the modular area.