Well 5 years is not a long time. Let's make it 15 years, then my thought would be that much less alts will remain until that time. I believe BTC, ETH and some top-10 coin will stay until that but many low market coins now will melt away.
Looking at the market cap of the top altcoins now and I think they can really go beyond 5years but not everyone will succeed on this challenges. But since cryptocurrency are slowly adopted by many countries I believe many altcoins will come to replace those who will failed in this market.