Samsung has just announced that they have begun mass production of 4GB HBM2 memory modules. When used on GPUs, four packages can provide 16GB of Video RAM with very high performance. They do this with a very wide data bus, which trade off frequency for transferring huge chunks. Samsung's offering is rated at 256 GB/s per package, which is twice what the Fury X could do with HBM1.
They also expect to mass produce 8GB HBM2 packages within this calendar year. I'm guessing that this means we'll see 32GB GPUs in the late-2016 or early-2017 time frame unless "within this year" means very, very soon (versus Q3/Q4). They will likely be for workstation or professional cards, but, in NVIDIA's case, those are usually based on architectures that are marketed to high-end gaming enthusiasts through some Titan offering. There's a lot of ways this could go, but a 32GB Titan seems like a bit much; I wouldn't expect that this affects the enthusiast gamer segment. It might mean that professionals looking to upgrade from the Kepler-based Tesla K-series might be waiting a little longer, maybe even GTC 2017. Alternatively, they might get new cards, just with a 16GB maximum until a refresh next year. There's not enough information to know one way or the other, but it's something to think about when more of it starts rolling in.
Samsung's HBM2 are compatible with ECC, although I believe that was also true for at least some HBM1 modules from SK Hynix.