Depends. Many altcoins are being driven up by the flood of money into cryptocurrencies so they will ride along with Bitcoin to a large degree as a store of value. Altcoins that have more practical applications to base their value on would probably still sink with Bitcoin initially but might be able to then capture more of the total market share. So in the long term if Bitcoin falls there's probably money to be made by investing in the right altcoins. But who knows... it's crazy right now.