For those of you who has been waiting for the RX 490 after AMD allegedly hints the arrival of the GPU back in July 2016, it seems that the waiting game is coming to its end. According to WCCFTech, AMD will be announcing and launching the RX 490 on the same day in this coming December, 2016.
AMD's current Polaris GPU maxes out on the RX 480, with performance that is roughly equivalent to NVIDIA's GTX 1060 6GB, we can assume that the RX 490 will deliver performance that goes on par with the GTX 1080, given that it's a card with dual GPU like what WCCFTech has mentioned.
Built specifically for VR, supporting resolution of up to 4K, bus width of 256-bit or even more, dual Polaris 10 or Vega 10 based GPU, and price point that is close to NVIDIA's GTX 1080 are some of the things that we can be sure of for now.
We've also attached the table from WCCFTech for your reference, which shows the rough estimation of the upcoming GPUs based on AMD's GPU roadmap: