Pretty conservative prediction, if you ask me.
As parabolic as the growth has been in the last few months, it's going to look linear compared to the growth rate once this hits mainstream, IMO.
In my own experience, around 1 out of 10 people have heard of bitcoin -- that tells me we're yet to achieve mainstream status, and we already are experiencing unmatched growth compared to other markets. Now, just imagine what it'll be like when 9 or 10 out of 10 people know what it is!