Some altcoins may have good potentials to grow in value but not all of them. Ethereum EOS, XRP are good altcoins Bitcoin on the other hand is the ultimate coin which has not yet been replaced.
Not all altcoins because most of them are just a weak coins who are here to make some money and not to give us good service. If altcoins is the best, why bitcoin is still on top? I still believe on bitcoin because of that and I know no altcoins can beat bitcoin, lets just buy good altcoins but never think that atcoins will go beyond bitcoin.