There is no such thing as Threaten anymore, if an enemy leaves a square adjacent to you without shifting or do anything that provoke OA, you get to do an OA. The only thing is that without the Sharpshooter PP, an OA is stated to be a Melee Basic attack which will more often then not, miss if you are armed with a ranged weapon (as at best you will be wielding an improvised weapon). Sharpshooter PP only make you able to make OA with a bow (and Ranged Basic Attack).
