Honestly, None. There are possibilities to things happen like bitcoin. in 2011 no one imagined bitcoin will hit $20,000. But It happened after 7 years. But people have to sell them at the right price. If they sell them at the peak point they had the chance to purchase 4x of bitcoin they Sold. So selling right time also very important same as the hold the coins.
Maybe in Altcoins also happen this. but we can't say it for sure. Ethereum is a good coin we can hold hopes I will stand for a long time. None of the altcoins I hold for forever.