Imagine how many more human lives could be simulated once such a singularity occurs than have previously existed in the realverse. Going into the future, if there is some reason to simulate human lives in great quantity, or just never-endingly (perhaps as some sort of living wikipedia entry), then simulated lives could outnumber 'real' (pre-singularity) human lives many times over.
So, given a machine / AI culture stretching on infinitely into the future, continuously simulating human lives for some reason, the chance that a person is born one of the 'real' unsimulated lives would be vanishingly small in these circumstances. So, whether or not one can find a 'glitch in the matrix,' which reveals whether or not we are actually in a simulation, it seems that one could imagine an infinite future of humans, with real humans (who may be completely unlike us) only occurring with vanishing measure. So in some (plausible?) futures we are almost certainly simulated...