Such "asymmetric warfare" can be very effective: if defending costs much more than mounting an effective attack, then an underdog attacker can keep on bleeding the better-resourced defender or even eventually force the defender to give up.

The use of COTS drones might not become a trend though, since jamming/spoofing the GPS and the radio frequencies used would prevent the drones from being directed effectively. Customizing the drone radios would add to effort and costs, and require somewhat specialized skills.