Eventually in the future, bitcoin will be replaced by another crypto currency but not soon. Bitcoin will be available till 2023 for mining. After that bitcoin will remain the costliest crypto currency. However, those who have already set up their expensive mining system, what will they do?

They will obviously find another crypto currency to mine and that crypto currency will become the next big thing after bitcoin. Everything in life, has a expiry date and bitcoin is no exception. But that is not going to happen anytime soon.