In 30 years? Probably much less than we think.

Think of the internet's impact over the last 30 years. You basically can't imagine life without it today.

And no one could possibly imagine its impact 30 years ago.

I think the same will be true of Bitcoin. If your guess is 21 now, I'd take the under, well under, if we were betting.

No one can know of course. But I think history proves that we have a tendency to vastly underestimate new paradigms, and it's impossible for us to see the new paradigm from within the existing one.