I think it will never happen. And Dollar and Bitcoin will live. These systems do not replace each other, but complementary. Everyone has the right to choose for him a comfortable system
Yeah dollar is the standard money we use in the real world and the bitcoin is the standard currency that we use in cyber world in every day transaction.But bitcoin cant replace dollar for now.
There is a lot of difference in that. You cant physically use bitcoin in an easy way which is really way too far from a fiat. There is no ease and convenience when making a actual trade like buying in a retail store unlike using fiat.