In my opinion altcoins will not be able to replace bitcoin as the number one coin in cryptocurrency. Most people would also think so. We know that altcoins were created to make up for the shortcomings that exist in Bitcoin, so it's unlikely that altcoins will take their place. From the name alone, altcoins are alternative coins which can be interpreted if they are used as an alternative, not the main one. But even though it can't match Bitcoin, some altcoins have good performance like ETH which is now being watched by many traders.