No way to know but it’s clear that TK isn’t interested in filling the unfilled vacancies for 756 FO EWR. Thus, I would estimate 2-3 years. Best to plan on serving your seat lock (2yrs) on reserve because currently the junior line holder is late 2018 hire. People on reserve can hold 737/320 Captain but can’t hold a line at 756 EWR to put it another way.