Always it is impossible to predict the future of altcoins, but at the same time block chain they were designed for continue to be used and developed, then the altcoins will continue in future also. Altcoins have a smaller investment when compared to Bitcoin. Many governments around the world are beginning to be legal to cryptocurrencies.
As long as bitcoin keeps doing halving mechanism and the chance for altcoin to increase will always there. The main important thing is since the inflation of bitcoin will have decreased due to the bitcoin halving and it will be also pushing the price to go up as soon as possible after halving has been happening. The futre of crypto will be surpassing gold. it will be achieved soon.