The AMD situation is probably even more confusing. The current lineup may get a refresh of some sorts but it doesn't look like we'll get anything new until the launch of Navi in 2019. And based on the latest rumors, Navi will not be a high-end chip but a successor to Polaris.
AMD does have its 7nm Vega 20, but at the moment there's no indication about a gaming variant of this part. The official roadmap brands this as a part for the machine learning market, but there are some fresh rumors now with a dose of specifications and speculation.
Vega 20 will get 32GB HBM2 and will support the new PCI Express 4.0 standard. TweakTown picked up word that the new chip has a die size of 360mm², a 30 percent reduction versus the Vega 10's 510mm² size. The site speculates the chip could offer compute power of over 20 teraflops, but take this with a grain of salt:
Vega 20 could benefit from around 55% power savings over Vega 10, or GPU clocks can be cranked by up to 40%, which would also see the now 4-stack HBM2 drawing more power. This would drive the Vega 20 card with 32GB of HBM2 to 400W, or more.
AMD could use a moderate 20% gain in GPU clock speeds and reach 300-350W with a performance leap of 65% all while saving 30-40% on power consumption. This would allow AMD's new Vega 20 GPU to beat NVIDIA's current Tesla V100 in compute at 300W with around 20.9 TFLOPs compared to the V100 with 15.7 TFLOPs.