While it is definitely possible, I don't see any other widely accepted Cryptocurrency other than Bitcoin today. That being said, I don't think it will happen just yet.
Time has shown that nothing is permanent. Bitcoin has gained considerable fame as it is the pioneer of the blockchain revolution. This achievement means that it will hold it's place as the leading cryptocurrency for a while. Nevertheless, new inventions will lead to new revolutions. It hasn't even taken long for Bitcoin to find it's rival in Ethereum so if the past and the present is anything to go by, Bitcoin won't be as hot a currency if new technologies come through soon enough.
bitcoin just like gold, silver and other natural resources can never be a successor, but bitcoin has the fact that they are a currency that can still be developed with the technology of innovation without stopping, so bitcoin will always get a strong successor candidate because of the very innovation competition strict. Bitcoin can lose and be replaced if in the end there is a cryptocurrency that is really regulated and developed by the world government.