Regardless of these considerations, Bitcoin or another decentralized cryptocurrency can never be the leading one among other currencies. She will walk predominantly between citizens. Whether it will be massively used by business structures will depend on how complete and favorable it is for legalization on the part of states. The states themselves are unlikely to use it very widely due to its high price volatility.
However, even by its nature, a decentralized cryptocurrency can walk in society only together with a common currency and cannot replace it.