How many BTC will make you a fiat millionaire ($) in 5 years? Why?
As I doubt bitcoin price will go totally insane in the near future I would say you will need more than 1.500 - 2.000 BTC to reach million dollars threshold.
There is probably no way that we will see price increase after the halving so it is hard to predict bitcoin price after that.
However when you look at how far bitcoin has come in the last 5 years and it's only picking up speed. Do the brakes even work? I think this one has none.

I'm going to be optimistic about this one and say it's 10-25 bitcoins.