Probably still very small, even 5% is unlikely.. it's only a bit more than 3 years away..
We are talking about the population of Earth and there are I guess 7.4 billion people already living today and on 2020 I guess it is not even going to reach 5% because 5% of 7.4 billion would probably closely to 370 million people. I think 3 years is not enough to reach that number of users of bitcoin on that year. I think still that would be close to 1%.
That's an aggressive prediction and i would say we are not that big, we are less than 1% of the world total population so if we are predicting for the total users for the year 2010 maybe at least 1% is a conservative projection.