I dont think bitcoin will replace dollar. Government always want some thing that they can control, and hold. Bitcoin cannot be controlled by anyone right one.
True. A currency which cannot be manipulated in terms of supply and value, cannot be adopted by governments. On the contrary, a centralized currency proves beneficial as central banks and governments could manipulate them to their own needs.
Bitcoin has everything that governments hate which is decentralization, where no external entity or third-party could gain control over how the cryptocurrency is distributed and its total supply. With this in mind, Bitcoin is far from replacing the dollar at any point in the future. Another thing that limits its ability to replace any fiat currency, is the ever-rising transaction fees and slow confirmation times.
With the dollar, we don't need to pay huge fees to transact with other people, and every transaction is made instant. But despite the inherent flaws available within cryptocurrencies like Bitcoin, I believe that they would co-exist alongside with government issued digital currencies.
The way I see it, is that the Dollar, Euro, and all the world's currencies will become digital empowered by private blockchains and distributed ledgers. Most recently, Russia has announced a CryptoRubble and Venezuela the Petrocoin. It should only be a matter of time before governments start rolling in their own currencies for them to co-exist with public blockchains such as Bitcoin and the rest of altcoins in existence. Just my thoughts