Im going to have to go with a conservative estimate of 5% of the worlds population will own bitcoin by 2020. 5% of the entire world population is enough people to create a country that has more people than the USA. There will definitely be more widespread usage of bitcoin as a payment method, and more governments will have to approve of bitcoin.
I think 5% for the estimated of the user of bitcoin for 2020 is very low because i think it is more than 10% now and it will keep growing because bitcoin is unstoppable and its price is keep on rising. The 3 years left will be enough for bitcoin to climb at least 20% of our population because we can see a lot of information that are keep spreading thru the internet and that will be a big help for bitcoin.
I think a conservative estimate would be like 5-10%. Bitcoin will be in the forefront in the next 3 years. Traders, investors or even the general public will keep growing their interest in bitcoin. Remember, Japan already started the revolution, so no wonder it has reached new heights now and will even soar more in the future. And also we also need to take in consideration the next halving in 2020. People will demand more of bitcoin but supply will be less. So more likely investors will try to get or put money in bitcoin ecosystem. So for me, a conservative estimate like 5%-10% but can probably rise in the next couple years of so.