Bitcoin prices are going up and down these days. People are hopeful that the price of Bitcoin may well go up by 2021. Bitcoin has been legalized in a number of countries, due to which Bitcoin prices are now recovering. If the price of Bitcoin goes up to 25,000 by 2020, it will be very difficult to buy.
Why it will be so difficult to buy, if you can buy some amount of it as you don't need or anyone to buy a 1btc if the price was high then wait for the price to go down before and for bitcoin to 2021 , i think its too way far for 2021 to predict whats realistic for me today is to predict or watch how much price bitcoin can reach this year due to halving season it also makes a higher price than 25k$ in my own opinion