By the time there are 21 million bitcoins, I'm not sure any of the currencies that it is valued in currently will even exist, and accounting for inflation over such a long period is fraught.
Using the Big-mac index, I predict that by the time there are 21 million bitcoins, a McDonalds© Big Mac© will cost 6 satoshis.
Yes I agree with the current number of the Bitcoin in the market are 21 Million. With this number we will experience the inflation in the price of the bitcoin. I am saying it of the reason with the increasing demand in the bitcoin and the demand will increase with the passage of time. Which will definitely result in the increase in the price of the bitcoin.