1 Bitcoin = $1,000,000 USD
21 Million Bitcoins = $21,000,000,000,000 ($21 Trillion USD)
The value of Bitcoin is never going to be that high, I think that we have to stay realistic and not speculate about things that we know are not going to happen.
I would be a great thing if the value would be that high but it is impossible to think that it will happen.
It would be really something if the price would be one million Dollar but a miracle would have to happen to get the price to be that high.
Do not get your hopes up for the price to be this high because the chance is small.