Since Motorola hasn't even provided monthly security updates to the unlocked Moto X Pure/Style, Moto X Play, Moto X Force, Moto G, etc., I have a hard time believing that they will provide regular security updates to the Turbo 2, unless it is a critical update. It's also quite possible that Marshmallow with the March security update (or the earlier update for the X Force) patches whatever the 2014 Moto X update is patching.
That said, kudos for the 2014 Moto X update. I'm glad to see the continued support despite deciding not to develop Marshmallow for the phone.