these systems are definitely coming. as someone who has some knowledge of this subject, it's worth noting though that there's a big difference between sifting through 36 million images a second and half the worlds population. these systems specified for a given number of population, the biometrics of that population are pre-loaded into the system and facial images are matched against those biometrics. the system gives results such as 'this image corresponds most closely to this biometric data'
i find it extremely unlikely that such a system exists with biometric data on half the worlds population. who has constructed a biometric database of that size ? there's simply no way
similarly, were such a system to exist with biometric data on half the worlds population then it would be matching at a lower speed simply because every image would have to be compared against 3bn sets of biometric data as opposed to a normal population size (e.g. 100 million).
that said, the technology is for sure at a point where e.g. police in an airport can facial match people going through security with biometrics for known criminals.
the first sign of a mass rollout of this will be when you apply for your passport and you have to use the states camera instead of providing your own photo.