Anyone claiming cryptos will disappear is talking nonsense and hasn't understood some fundamental property of crypto.  This isnt hard bullish sentiment just simple observation: crypto's dont die.  Thats why there are 1600 of them listed, all sorts of scams, whitepaper projects, hobbies and jokes are in there.  Bitconnect is still exists and still trades!  Verge coin is valued at $300m despite being hacked and having no meaningful development team.

Once released a crypto will survive as long as the code exists and running somewhere. The question is whether there is any value in the market.  Most of the top 100 wont offer real value in the future, as people and tools coalesce around a small group.  This has to happen for the the mas market adoption, people aren't going to use it every day with so many competing coins and technologies.  Cross-chain solutions wont solve that because people will want a simple concept of $crypto is worth $currency not have to track multiple exchange rates. Dapps and tools will flourish in high numbers, however they aren't going to be used as currency, they can exist on or adpot other established blockchains.  

We like to compare to the early Web, the dot com era of the late 90's, however technology wise we are in the early internet era pre-web, where lots of competing technologies via for attention most of which are rubbish some of which are fantastic but will be overlooked and a few of which are the future foundations.