I don't think it will take 20 years. I think things will move a lot quicker than that. And I also think that there are enough ideas, concepts, and cryptos that you can offer decentralized, centralized, and possibly a hybrid for each user based on their wants and needs. Each coin/token represents a different community and with that community a different thought/belief ideology. Obviously each would have their own unique advantages and disadvantages, without any one coin holding all of those aspects.