Everything will have its end, so will bitcoin. But, we don't know exactly when it ends or when the price gets down. Time will answer it.
And there is a possibility for another cryptocurrency to take over bitcoin since there are a lot of new cryptocurrencies appear and compete each other.
I don't think so. Everything doesn't have ends, for example paper money. It doesn't have an end. Bitcoin won't have an end too. It's not a living organism then it can survive forever in the market.