1) Current AI tech is already nearing the top of the S-curve. In this case it will do nothing to help humans in the "real world", it will just replace much of the human labor currently used to create/manipulate bits.
2) Current AI tech is near the bottom of the S-curve. It continues to ratchet up and its capabilities become super-human, as you outline. In which case, how long until the AI capable of creating self-replicating machines realizes it doesn't need to listen to humans anymore, or even keep them around?