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.
That's a pretty modest set of parameters for success. It can pull that off with ease even with the current creaky infrastructure. Some seriously slick stuff is on the way to replace it, though.