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.
Thank you for your answers.
I also think if bitcoin dies because of loss of attraction and consumers. ETH will take over Bitcoin because we know that ETH is the most popular after Bitcoin. how do you think about that?
It would be very difficult from investors point of view to lost our attraction to bitcoin. Unless in extreme cases that suddenly we all shift to altcoin market and totally abandoned bitcoin. But its less likely to happened. ETH has already attempted to overtake the spot from bitcoin if you would remember. There was even a time when the marketcap of ETH was almost the same as bitcoin and people started to talk about the 'flippening'. Unfortunately, ETH bubble was burst, so it didn't happened. So I don't think that ETH can really replaced bitcoin as the dominant coin, unless we all shift to ETH and government around the world connived with its other to banned bitcoin.