Regarding the Wow flights, it looks like a number of other airports are being put in the same situation as Cork, with Bristol, Dusseldorf and Lyon all suspended for the Winter and not showing for next summer. It's also worth noting that frequency to Dublin seems to be reduced.
The main problem seems to be an imbalance in seats out of KEF to North America and Europe. What that has meant is that those airports where there is limited point-to-point demand to KEF suffer because there aren't enough available seats (or maybe enough available seats at a reasonable price).
They seem to be remedying that by using the freed up capacity to introduce new destinations in the US Mid-West (although not at times that are great for connections in KEF, so we'll see how that goes).
With extra aircraft on order and new North American destinations to be opened up, I wouldn't rule out the route returning at some point in the future. I doubt it will be in summer 2018 though and at that point they may as well wait to 2020 when the clock resets on route incentives.