I've been watching some of the preview videos posted in the previews thread and saw a loot box!
Item description: Contains one random weapon or shield. Opens automatically on purchase.
https://youtu.be/2yqQer3XhKs?t=2m30s at 2:30
It's called "Heka Chest" and according to Wikipedia, Heka means magic in Egyptian. I don't know if that's a type of several other types or they're all called Heka Chests. It's labeled a "Mystery Item" which could mean there are other mystery items in the game.
Seems like you can only buy them with in-game currency, in the preview build at least. I bet the final build will have Helix credit.
Nerf my drop rate if old.
EDIT: Nothing is confirmed yet and AC games have had MT in their games for a long time but none affected the game. I hope Ubi clarify this before release.