I guess it will be difficult to find an answer to this. We can never really tell how many people is added every day using bitcoin. Unless we do have a proper enlistment of everyone or something to monitor the people in it. But as of now I think more and more people are using bitcoin.
we can only see the movement of bitcoin users from selling and bitcoin buying activity on each exchange. It will be difficult to ascertain the exact number of people using bitcoins. Perhaps this isn't very important about the data collection of its users. We just need to spread positive things about bitcoin so that users always go up from year to year.