In line with expectations today some new rumors surfaced on the mighty WWW. AMD possibly will have its first Polaris based series 400 Radeon graphics cards available in June, this would invoke the R9 490 and R9 490X. It is likely that these cards will be on display at Computex.

From what we heard, the Radeon R9 400 series will indeed get gddr5x memory, Micron (who delivers this new type of memory) already spread word that it is in volume production ever since srping. The AMD Radeon R9 490 and 490X graphics cards will be fitted with a Polaris 10-gpu, aimed at the high-end segment of the desktop market. Polaris 11 would be the GPU series specced for lower class graphics cards.

It  was AMD themselves who in a recent roadmap was showing that polaris would be avilable this year during the Capsaicin-event at the Game Developer Conference. 
 

Obviously AMD has not shared any specifications so all this remains unsubstantiatied including the memory type and naming. The roadmap also disclosed that you can expect HBM2 based product no sooner then early 2017. 

Rumor: AMD Radeon 490 and 490X Polaris graphics cards launch end of June