Top 5 altcoins will surely survive no matter what the future may hold. There are tons of money involve that every developers, investors and holders don't want to lose.
Altcoins are basically alternate coins (i.e. alternate to Bitcoin), and there are above 1,000 different altcoins lately. Of course, most of them will crash and burn and maybe less than 50 will survive. Who knows? No one can predict what will happen in the future anyway.