I see the world is moving in a direction where it will be divided in two sections, one would be US supported countries that will continue to use the dollar as their main currency. The other block will be forming as an Anti-US country that may use Bitcoin as a main currency to trade/deal between them.
The replacement of USD as a reserve currency will likely happen eventually unless China gets defeated badly in the geopolitical games. But there's close to zero chance that it'll get replaced by Bitcoin.
The world's reserve currency will be the currency of the country that dominates economically (and militarily).
I wonder if US is actually capable and willing to do anything to prevent that from happening.
I will be in the opinion that they will do everything in their power to maintain USD as the dominant reserved currency. Although there are a lot of movements right now, BRIC thinking of another alternative currency to be used, or as someone mentioned, Saudi might try the Yuan. US is still capable to do that, maybe offer trade baits for other countries, or improved their trade relations so that they can keep power of the USD.
As for bitcoin or any cryptos to be a reserved currency, it should be stable, which obviously is not a trait of
BTC. And for Yuan to be a reserve currency, it should have depth and liquidity, and their financial still lacks that.