Not almost everyone but merely 98% is using bitcoin on that year.because in this era we are living technology is rising,and by the help of this bitcoin will be more popular in every year that will past.
I think that's too much. the current bitcoin users may not be more than 2% of world population. if the user bitcoin is big enough today. maybe now you can see many traders around you who will accept bitcoin? but the reality is not. bitcoin users still quite a bit and you can see the very rare people who accept bitcoin
It will depend on how people talk it by mouth and spread the words about bitcoin and also depneds on organisation,media and big businesses if they will accept bitcoins and advertise it on general public well in that case bitcoin would provably be used by majority of public in year 2020,
But if this current state for bitcoin will be implemented? Well i dont think it will be happening since their are various countries banned bitcoin for their usage since they know bitcoin in illegal ways.