I am not sure what the price of the coin will stop at. Maybe the coin will be a million dollars each, that would make 21 million people millionaires if they all held a single coin.
Frankly, I know it is a joke when people say bitcoin will get to a million dollar per coin. There's no way this is going to be possible because we are dealing with the issue of supply and demand. Already, people are shifting their attention to altcoins which serve as payment medium like litcoin, monero, dash etc because of the unending transaction fees of bitcoin. Attention is already shifting.