Bitcoin offers a complete alternative to the current monetary standards and thus it adds a choice that wasn't before available - to invidivuals, companies, nations, etc... It is not a direct undermining or a direct challenger - it is a disruptive answer to the question of "What is money?" and as such could (and likely will) disrupt all other monetary systems present in the world - but how long that will take is very hard to estimate.. Disruptive technologies tend to be exponential and their tipping points occur very suddenly and unexpectedly.