Never. This is impossible
Although it is really hard to believe that Bitcoin can cost a million, it might happen. However, many years will pass, and for this only a few BTC should be remained.
The only time Bitcoin will be worth $1 million dollars is when the USD is worthless. I mean, i'd love a million per Bitcoin, but that would put the market cap at a staggering $17 - $21 trillion. Golds market cap is $8 trillion. Bitcoin hitting those numbers are very unrealistic. $100k per bitcoin is within the realm of reality though.