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.
It's a fact that it is not going to be replaced by another crypto currency. The market cap itself will give us a clear answer that other coins doesn't have match for replacing bitcoin on it's current place. There's no way for now that bitcoin will be replaced by a new crypto because all of them are just depending on it.