price of $1 000 000 per bitcoin very soon. Let's just take the growth from last year :
2016 - 2017 ===> $3000 increase {more or less and this was pretty impressive}
Let's predict the next 5 years, with a $3000 increase/growth per year :
2017 - 2018 ==> $ 9 000
2018 - 2019 ==> $12 000
2019 - 2020 ==> $15 000
2020 - 2021 ==> $18 000
2021 - 2022 ==> $21 000
So this is nowhere close to $1 000 000 per bitcoin... right.
There are many factor to determine the rate of increasing the price, What you just used was the difference from last year's price to this year's.
Since Bitcoin is not used as a currency yet and can be more considered for now as an asset that can be traded to a fiat currency we also need to consider the increase on the number of people who is into it.
So if last year there are only 10 million people who is into bitcoin and this year its 15 million that caused an increase of 800% on price per coin. (~$639. to $5492) then how will the price be when 20 million people accepts the coin, when 25 million, 30 million.
It is really hard to determine the coin's maximum potential because of its anonymity no one knows if how many different individual owns the 16 million + coins.