Terminators Will Happen
There is no doubt whatsoever that there will be robots programmed to go after someone and kill them. By that definition they probably have been used already.
Even a drone hobbyist could conceivably deploy a GPS enabled flying drone to go to a destination and explode. Adding sophistication to that scenario, a hobbyist drone could search precisely for the victims by their mobil phone ID. Or by facial recognition. These technologies are available. And so, they will be used. Whatever is possible will be done.
So, Terminators will be here. The longer term question of course remains: Will they ever become aware and turn on us ? I guess we’ll see.