How sure are you that BTC will succeed?
Let me elaborate.
Succeed as in it will reach $5,000 or greater and it will reach main stream adoption.
As for figures, let us just say at least over 20 Million users from the current estimates 2-3 million users as of March 2014.
As for time frame, lets say within the next 2-3 years from this post's date.
I think those numbers and the time frame are pretty meaningless. If Bitcoin is still around in 10 years and has 100+ million users, we will know it has at least succeeded in becoming an established niche system.