I would say there is a good chance you will be booted from the seat. COPA does indeed have rules that limit access to the bulkhead and exit row seats to higher fares/premium flyers. In my experience, the COPA site operates in an inconsistent manner, and I am not surprised that they would show you a seat for which you are not eligible.

(NOTE - It may be the case that W fare is eligible for premium seats, as it not that far down from the top.)

I would call them and get your seats locked in over the phone. If they can confirm the exit row, then great.