While the discrete GPU market is declining in terms of volume, the enthusiast portion of the market is thriving. In 2015, shipments of enthusiast graphics cards doubled to 5.9 million units. Much of this increase, I suspect, was due to NVIDIA's GTX 970, a graphics card launched in late 2014 for $329 that has been a massive success for the company. Despite its high price, the GTX 970 is by far the most popular discrete graphics card in use on the Steam PC gaming platform.
AMD's plan to focus on the mainstream GPU market comes at a time when the market is clearly shifting toward the high end. NVIDIA was able to pull PC gamers to higher price points in 2015 with the GTX 970, and the company is looking to do it again with the GTX 1070 this year. If all of AMD's Polaris graphics cards are priced below the GTX 1070, the company will need to offer compelling performance in order to prevent the same thing from happening this time around.
AMD's bet on mainstream graphics could backfire if Polaris falls short of expectations.
http://www.fool.com/investing/general/2016/05/18/amds-bet-on-mainstream-graphics-could-backfire.aspx