Well yeah a lot of them will die but as long as there is demand there will be altcoins. Also, altcoins are cheaper, so people who haven't invested in BTC yet will prefer to invest in altcoins first
There are still altcoins will survive the market is very active, so there are some altcoins are dead. And there are altcoins survive because of continues demand. Yes invest or choose altcoins that is profitable in the long run.