I don't see how we're going to get seven billion people to use bitcoin one day. What about all the people without an internet connection or those who can't afford devices to obtain a wallet and send/receive btc? I can imagine something where a lot of people could wear bitcoin related apparel to boost the bitcoin awareness. You could try get shirts sponsored and have a public get together where everybody could be wearing something related to bitcoin. Maybe something like a mask would do like the Anonymous marches and conventions.
people without internet access, will be connected when google "loon for all" project will be ready, but i'm afraid this won't be enough to make everyone to use bitcoin even for one day, many still don't like the fact that early adopters were lucky, and they must buy from them
Loon won't be available worldwide and if the is going to be, it won't be very soon. That still doesn't solve the problem with the people without devices. I still think an awareness convention would do well.