At first, I had similar thoughts as MD on this: Trading people could open the door to more people being captured/held in the future for negotiations...One of the key reasons we shouldn't negotiate with hostage takers...
However, with a little research and looking at the "big picture", I've changed my initial opinion of it...First, this isn't a hostage situation, it's a war situation and these are prisoners of war...It's also common to trade prisoners of war when it's over, and this one is coming to a close...Lastly, to me, this is good policy because it promotes safe treatment of prisoners in future wars...If a rouge group knows there would never be a chance of getting their people back in a swap, why not just kill the POWs right away instead of dealing with them for all those years?