Current drones are very limited compared to what they could do with a lot more processing power and future hardware developments. E.g. imagine a drone that could shoot a moving target hundreds of metres away in the wind, while it itself was moving very fast.
"Large" drones (aircraft rather than quadcopter) seem to follow the same rules as manned aircraft and engage with guided or unguided munitions of their own. If the drone is cheap enough then "drone as munition" seems likely to win.
