As this does not appear to be a, let's call it "Skyrim or Fallout" based approach to NPCs (that feature a large number of unique NPCs actually housed or put somewhere with simulated schedules), this is more of the usual open world city approach where NPCs, at least non-unique ones, respawn.
It only makes sense in such a packed city. You can't obviously simulate all of them at once for performance and possible gameplay reasons. Is it fun to bump into people left and right constantly in very packed and visited places? I dunno, maybe not after countless hours of trying to get around on foot, or driving on overpacked streets.
So the alternative in simulating a large city is basically an adequate number of NPCs depending on location and time while having an endless amount of them. This might be handled differently for remote areas where you can likely thin out the herd there in more apparent fashion, but I reckon if it's non-unique NPCs they will respawn as well eventually, like badland raiders.
It will just feel more like thinning out the herd because the respawn countdown will be higher compared to the inner city plaza as example because losses would be quickly "replenished" there.
But in the end, it's wait and see. One month and a bit, then we can test it ourselves.
But long story short, as not literally every NPC (even non-named ones) are fully persistent throughout the game and in their respective locations or simulated and thus "finite", you cannot turn the city into a ghost town. That would not be intended anyway even if it might be funny to try.
Devs already said running amok will eventually put to a stop by force escalation of corporate security and city police forces meaning you wouldn't survive running amok in the city.
