I wrote before that future air war will widen to include both sub-aircraft very low level small drones (even bird- or flying squirrel-like) and almost exoatmospheric high cost aviation. Air forces appear to be interested in the latter more than the former, and hardly anyone ponders the consequences of conventional "air superiority" fighters being perfectly pointless for the air campaign at small scale and (typically) low altitude.
A € 100+ million aircraft with € 1+ million missiles and a single autocannon to be used at speeds higher than 400 kph is not going to be relevant to the question whether an army brigade will be slaughtered by the onslaught of 50,000 bird-like, largely autonomous and cooperating drones carrying a 250 gram warhead each.
Our equipment is not only woefully inadequate to defend against such an onslaught. We would likely fail to make good use of it if we had, for given flight technologies as shown in the video above the identification of targets is going to be extremely difficult. It will be fairly easy to mimic the speed, flight behaviour, thermal signature, radar signature, altitude, noise(lessness) and visual spectrum of a bird in the 2030's at the latest. It will also be possible to use the protective effect of a swarm or herd; 2D sensors will probably be unable to track an individual in it. Feigned "deaths" may happen as well with such slow flying objects, provoking a premature interruption of the engagement sequence.
Large military development programs appear to require at least 15 years to maturity, so we should begin now to prepare for the 2030's - and I'm not talking about ballistic missile defence here. We've had enough attention on the expensive, high & fast threats. We need more attention on the lowest layer.
The air forces will likely institutionally fail a this challenge, so it will be up for the ground forces to rise up to the challenge, develop and introduce into service the air defence of the 2030's.
It will be interesting to see how they will cope. My guess is that a bunch of countermeasures (such as EMP) can provoke counter-counter-measures, thus driving up the size and cost of individual small drones to the point where target detection, identification and defeat will be practical enough to achieve a new equilibrium similar to what it happened after the debut of attack helicopters. We will likely see something that did not quite appear among helicopters; dedicated air-to-air systems, the equivalent of raptors.