I wouldn't bet any money on this happening but I also wouldn't be surprised to see this happening. Hanifin, Provorov and Werenski are all excellent 'D' prospects, and any one of them could end up being the best of that group fantasy-wise. That's why I wouldn't draft a D-man in the Top-5 but rather trade down if I wanted a D-man.
Back to the original question; yes, Konecny could be a nice sleeper if he falls further than 15th in anyone's draft.