I mean its only 21million btcand there are 6billion people in the world , how can it be enough
Just think about the number of people that will be using bitcoin in the future, we can not be able to determine if the whole pulation will use bitcoin at this time and for sure it is not 100% of the entire population will adapt bitcoin . Also, not all people will be able to obtain 1 bitcoin easily so I can say that 21 btc is enough .
i think that in future most of the people will be using bitcoin. as we can expect that in future the price of bitcoin will increase too much and hope that in such time we will count bitcoin in satoshi as because of its high price.