Well, clearly the owners of robots are unlikely to risk losing their capital by assigning their valuable property to tasks in which the robots face the probability of being blown up. So, it is likely that the fate of the poor will be to serve as soldiers in the various armies of the future - whether revolutionary or counter-revolutionary, imperialist or anti-imperialist. Cannon fodder. Except in peace time when they may be kept docile with bread and circuses. If there is much peace time.

I have no idea why you think that the cost of feeding a human soldier, even if you sent him to the battlefield naked and unarmed to fight other waves of human flesh, would be lower than deploying a drone.

Population reduction tempered by charity efforts by the robot owning humans seems more probable. Also over time the majority of non-robot owning humans might be part of feral populations if there is any natural habitat left.