I'm not sure if Motorola will support this feature, but Marshmallow will allow you to format an SD card as adoptable storage. So, if you have a 32 GB storage Turbo 2 and add a 32 GB SD card, if you choose that option the phone will act like it is 64 GB of internal storage.
Of course, that will mean reformating the card, and it won't be usable in another device until you format it again. And, there is no support for it now.
SD Card storage on Android is a bit of a kluge. You can storage data there, music and videos, etc., but not all apps support looking at SD card storage. But - if the idea is to add a ton of music and movies, it's a great option.
I personally like the simplicity of internal storage.