I think it's 2 millions of members that we have right now, or more. That is only to my rough estimation. And in my observation we have member here that has multiple account in bitcoin talk.org meaning the 2 millions can possible to multiply in to 2 or more.
I do not agree with you. I think there are at least 10 million people using bitcoin at the moment. In my country, although there is a law of bitcoin using restriction, more than 100000 people are having bitcoin in their wallets. And currently, more and more people are willing to learn more about bitcoin, to see what bitcoin can bring to our life and to seek for bitcoin advantages. Therefore, i think, there will be more than 1 billion people know about bitcoin in the future