By the end of the 14-15 season there were two options. Trade him coming off a somewhat down year, with just a year left until free agency, or, sign him. Could've squeezed out one more year from and just let him walk after last year too, so three options. Lucic at 50% got the Bruins a mid 1st round pick, a young defenseman, and eventually another 1st round pick, which ended up at the bottom of the 1st round. Figure Kopitar is better than Lucic, and he's a center, so Kopitar at 50% probably brings back at least a little more.
You'd want at least a top 10 pick in return. Any teams with top 10 picks at the 2015 going to trade for Kopitar? Edm, Buf, Ari, Tor, Car, NJ, Phi, Clb, SJ, and Col had those picks. NJ? Columbus picked Werenski. Kopitar to the Sharks?
Any contending teams in a position to trade for Kopitar at the time? Probably won't get a good young roster player, as those teams would want to add to their roster, not just create a hole to fill a hole. The top prospect in their system for a soon to be UFA? Even Lombardi hasn't done that.
No way to know what trades could or could not happen, but where's the pot of gold? I guess anything is better than $10m in cap space for maybe 15 goals, even just allowing him to walk out the door on July 1st.