Last week some fresh AMD Navi rumors popped up on the Asian ChipHell forums. As always, I suggest to take these rumors with a grain of salt. We can't verify the accuracy, and a manufacturer's plans are subject to change.
Anyway, here's a brief overview:
Navi to have surprisingly low power consumption versus previous-gen AMD designs
No ray-tracing support, which is not really a surprise
Navi to target lower price points
Launch expected in Q2 or Q3 2019
Performance claimed to be competitive with NVIDIA GeForce RTX 2080