It's new. If it does become our nouveau de facto global currency, it will first become an intermediary for traditional currencies to facilitate transactions. Buyers will exchange their dollars and euros for Bitcoins, and sellers will largely exchange their Bitcoins back pounds and krona (or whatever).

However, the more people accept Bitcoin, the more people can spend it. There will be a network effect. Eventually, if this pattern holds, the food producers will start to accept it and that's where the "trouble" occurs.

In theory, if people perceive the stability, utility, and value of Bitcoin to be greater than a traditional currency, and it starts to replace that traditional currency, the traditional currency will collapse, hyperinflation will occur, and there will be a period of pain. The late majority and laggards will lose a lot of money, and the early adopters and early majority will gain. There will simply be a redistribution based on tolerance for risk and foresight. At this stage the value of Bitcoin will soar.

Frankly, I wouldn't be surprised if governments did their best to make it illegal. Governments don't entertain competition because their role is to maintain the stability of the status quo, which is fair. We all enjoy living in a degree of stability, as opposed to a Hobbesian state of nature.