This is never going to happen anytime soon.
Dollar, cash, goverment money is going to be here for a loooong loooong time.
Very sure that this is not going to happen. They can consider bitcoin as alternative payment for those people that don't want to use cash for their payment. And whether bitcoin will replace dollar or not, bitcoin is bitcoin and it is as it is. We love the way on how bitcoin is growing, we love the way on bitcoin is being adopted and this is one of the very few reasons why bitcoin is better than dollar.