Cryptocurrencies are currently technology-oriented but in the future, they will be community-oriented (based more on human principles) and coins will periodically upgrade the underlying technology to improve performance (so long as the wallet address system and account balances are the same).
Different cryptocurrencies will fluctuate in value relative to each other depending on the economic input and output of their communities. The input and output of a crypto-community will vary depending on the appeal of its human/social/political principles; the means of production will bind to cryptocurrencies which follow the principles of those who control them. A cryptocurrency which has an aging community and whose value is supported by legacy systems will slowly lose value.
A person will always have to keep moving their wealth between different cryptocurrencies in order to maintain it. They will have to know and adapt to all the economic trends and changing societal values in order to know which cryptocurrency/communities to invest in.
Staying rich will become difficult; it will require a deep understanding of changing social trends and principles.