I think it is more useful to imagine bitcoin as an internet success, not a world revolution. If bitcoin were as successful as a facebook, or a twitter, widespread, ubiquitous, with apps on smart-phones and bitcoin addresses shown on billboards and so on. 21 billion dollars in bitcoin trade would make the 1000 dollar bitcoin about right I would say. I'm not sure how a 21 billion dollar bitcoin economy compares to something like facebook advertising and data-mining revenues annually. Perhas it would be necessary to talk in terms of estimated bitcoin GDP.