That is too optimistic. It will be unlikely the majority of the people around the world use Bitcoin.
It can happen only in an apocalypse-like scenario. Imagine a situation where all the fiat currencies in the world loses their value. In such a scenario, only de-centralized currencies such as Bitcoin and bullion coins (gold, platinum, silver.etc) will be used as currency.
If something apocalyptic should happen, Bitcoin will be the first to kick the bucket since it doesn't take much to bring down the network. But without Internet Bitcoin is as useless and worthless as the dirt under your fingernails. In fact, just disrupting the Internet integrity for a long enough time (say, a few months) will most likely suffice to check it out. Paper money seems to be more resilient and durable in this respect and may last a little longer after governments disband and disperse...
But ultimately all paper will burn