Bitcoin is a very popular crypto coin today, we know that Bitcoin will be very expensive in the future but I imagine if Bitcoin die, whether there will be hope for the future of altcoin? because most altcoin exchanges are to bitcoins
your opinion is highly appreciated.

It might depend on the reason why Bitcoin can die. In case when the death is due to total ban of Bitcoin as done by all governments or regimes then there is a possibility that Bitcoin death can also mean the death of altcoins. Now, if the reason can be other than that or it is within Bitcoin like losing the appeal from the market then there is a possibility that another coin can rise up to take the vacuum of leadership.
Very interesting point. The scenario almost requires that all global governments unite into a authoritarian regime. As it stands now I don't think that is very likely. Fiat currency opened the door for digital currency. In democratic countries it would require a fairly sweeping crack down and in some cases reversal of course as some governments have already signed on in form of policy guidance to the acknowledgement of cryptocurrencies as an economic instrument.