I don't think that bitcoin will be ever replaced by any other crypto currency as I don't see any competition to bitcoin at a moment and even in future bitcoin will keep on updating itself with the demand of people so its hard for any crypto to replace bitcoins.
There is no competition for bitcoin at a moment but it can be changed in future when new technology will arrive and at that time there is a possibility that bitcoin can get replaced by other currency.
i think bitcoin is the most popular currency as majority of people are using it and as you think that in future it could be replace by new currency with the arrive of new technologies, well so i think that when in future the new technologies arrive so bitcoin will also adopt these technologies and update its self.
although everything is possible and bitcoin can be replace by any other currency but still i will like to add that as bitcoin is still the number one currency of the world and people from all over the world are investing their money here therefore in current position not a single currency can take its place and may be it will really take a long long time.