if internet goes down, sure there is no life for bitcoin and all the bitcoiners will be found upset.. but that won't happen very easily.. by chance if internet is lost, we can regain it and can give life to bitcoin again...
just a one thing will not change everything. It will be hard for that to happen. Bitcoin is a global currency, and has value more than U.S dollars, lots of people prefer Bitcoin, because, Bitcoin is versatile, and being versatile is what makes the value of Bitcoin.