Apart from few announcements for the mobile market and long-term GPU architecture roadmap, no details were revealed about future products by Radeon Technologies Group. The RTG is currently focusing on Vega, or more precisely making it available. Scott Wasson, who was interviewed by PC Games Hardware confirmed that the company is now making custom designs a priority, so the shortage of reference cards may be permanent.
Scott refused to more specific about the future Radeon products, but he did mention that next generation, which is Navi, will be available after Vega 7nm (which officially only goes into Radeon Instinct). The sampling starts later this year, but it seems unlikely for actual products to be available in 2018.
Gamers who wish to buy Radeon 600 series cards may need to wait a bit longer. AMD could potentially launch smaller Vega and replace Polaris 10 GPU, or launch Polaris with GDDR6. Whichever option they choose, it has not been confirmed yet. The worst scenario means no Radeon 600 this year.
°Looks at current graphics card prices, sees lack of stock of any graphics cards of any decent power° I think Bender put it best: