No, because as you can see that the bitcoin is an online money or digital currency so by that, it means that it needs a requirements before you will use it for example a internet and a gadget almost all of that have that but some are didn't have that the poor section of the society so by that it means that not all people can use the bitcoin and that is the reason why bitcoin can't replace any fiat.
Yes, bitcoin without the Internet can completely disappear and because of this can not become a substitute for the dollar. If over time it can operate without the Internet, then it will be possible to talk about the possible ousting of the dollar.
we can't really know what will happen. it may go two ways. if we progress more in the future then possibly btc can emerge as the number one currency used. if we succumb to war and most that we know now disappears, then I don't think even the dollar would have much worth to that kind of future.