AMD seems to be focusing on squeezing as much out of its Polaris architecture as possible while we wait for Navi to arrive. There have already been several generations of Polaris parts, including the Radeon RX 400 series, Radeon RX 500 series, and a refreshed release of the latter. Now there is chatter of a Radeon RX 590 model being around

Source: Hot Hardware – ASUS Reportedly Prepping Radeon RX 590 ROG Strix Polaris Refresh Graphics Card