Yes, 1 Bitcoin will be enough for most people if they can hold it for next 20-30 years. The price of Bitcoin can grow very high in value and some people like Michael J. Saylor think that 1 Bitcoin could be $5 million in value in future. I believe that $5 million is a sufficient amount for a lot of us and if his prediction becomes a reality then everyone who holds a Bitcoin would be among the millionaires.