PC Perspective had an interview with Raja Koduri, the SVP and Chief Architect of AMD's Radeon Technologies Group. One of the things they talked about is how AMD is aiming to get past CrossFire with the new Radeon Pro Duo card. Koduri explained getting multi-GPU hardware in the hands of game developers is crucial as the company's future lineup will contain smaller, more power efficient GPUs because the economics of the smaller die are much better.
The implication here is that we're going to see a lot more multi-GPU products in the future, not just in the enthusiast segment but across AMD's entire GPU portfolio.
With changes in Moore’s Law and the realities of process technology and processor construction, multi-GPU is going to be more important for the entire product stack, not just the extreme enthusiast crowd. Why? Because realities are dictating that GPU vendors build smaller, more power efficient GPUs, and to scale performance overall, multi-GPU solutions need to be efficient and plentiful. The “economics of the smaller die” are much better for AMD (and we assume NVIDIA) and by 2017-2019, this is the reality and will be how graphics performance will scale.
Getting the software ecosystem going now is going to be crucial to ease into that standard.
The site also notes that even though Koduri didn't confirm it outright, it looks like the Polaris GPU architecture will stick to first-gen HBM memory:
Why is Polaris going to use HBM1? Raja pointed towards the extreme cost and expense of building the HBM ecosystem prepping the pipeline for the new memory technology as the culprit and AMD obviously wants to recoup some of that cost with another generation of GPU usage.