FUD Zilla had a chat with anonymous industry sources and got to hear that HBM2 memory is still in very short supply and very expensive. The sources claim HBM2-based video cards are unlikely to arrive anytime soon, both AMD and NVIDIA are expected to stick with GDDR5-class memory for the time being.
The first card with HBM2 may be AMD's Vega (Greenland) or a Titan card from NVIDIA but these products aren't anticipated until late 2016 at the earliest, or sometime in 2017.
It seems that GPUs of 2016, including the new AMD Polaris and the new Geforce, will be stuck with GDDR5 and in best case scenario with GDDR5X from Micron. The word on the street is that both Geforce GTX based on Pascal and AMD/RTG's Polaris 10 / Ellesmere and Polaris 11 / Baffin might launch at Computex during last days of May or early June 2016.