I do not see bitcoin helping the world economy but rather it can help an individual economy. Obviously, every country will not legalise bitcoin but the individual economy that adopts bitcoin can push in a huge investment when bitcoin is down to get some accruing profit from investment when price go up. By such profit, the individual country can better her nation and her people by providing more social amenities, building projects, factories and employment.
I agree. If one single or individual economy adopts bitcoin the tradings of money, specifically dollars will help for the improvement of it. It might not be a big step but it's a stepping stone for improvement.