>100 bitcoins. Will I be a millionaire by 2020?
No.
Why not? bitcoin prices are always unpredictable, as we now touched $500 in a short time. so in 2020 may be 100 bitcoin be a millionaire, if the price above $1000

you need 10k to be millionare if you have 100 btc, and millionaire mean at least 2M right? so you need bitcoin to reach 20k, really hard imho
if I have 100
BTC and the price in 2020 was $1000, it can be said that I have become a millionaire in my country.
if we wait for bitcoin prices so high it was difficult, so you may need to have more bitcoin.