Its already happen in several weeks ago. Most altcoin price drop the bottom level. Ethereum price untill below $200 and others altcoin cut the price more than 90%. I am keep buying on some good altcoin and right now many of that altcoin already increasing the price
If you are sure that the token that dropped in price is reliable and think that it was a temporary fall, invest in these altcoins. Then wait for several months until the alts you have can start gaining again.