Do you think Bitcoin will remain the most dominant coin both short and long term? Even though it does not remain the most dominant coin, this will not be the same as saying that Bitcoin wont exist long term.
Of course BTC will remain dominant. Although BTC prices decreased but a few months will recover. A recent price change shows us that the price of another coin is related to bitcoin, but even though bitcoin decreases it takes several years for another coin to go beyond bitcoin.