best guess, medium Polaris, anything from 15% slower to 15% faster than a Fury X by June(depends what sizes they come out with early on new process), medium Pascal, more like Sept/Oct. Fury X2 to come out at some point which should be good. You obviously know all about dual gpu cards. DX12 should make dual gpu cards run significantly more consistently across games. As in, the majority of DX12 games should do well with multi gpu, scaling might be better but xfire scaling is frequently brilliant anyway.
Medium polaris likely to be more like 125-160W range, significantly more efficient, extra DX12 features, extra other features like DP1.3. So I'd think about 2-4 of those personally over Fury X2. If you're going to want a 120-144hz 4k panel, or an HDR panel, then you want Dp 1.3... although it is possible Fury X2 will have it added.
Big Polaris/Pascal almost certainly not till 2017, so the true Titan/Fury X successors with maybe 70-90% more performance won't come till next year.
