I guess this will be built on so called private Blockchain.
A Blockchain isn't really a Blockchain without being immutable, permissionless, censorship resistant, decentralized, transparent, anonymous, trustless etc.. In my opinion, if your Blockchain does not meet up 50% of this standard then it's not worth being called a Blockchain. Better they just stick to normal centralized method for "better experience".
Exactly. The Blockchain without its key characteristics (immutability, censorship-resistance, and decentralization) cannot function as intended. Centralized digital currencies would look more like databases instead of a real blockchain. That's the case nowadays with Ripple's XRP where the company controls the whole digital ledger as we know it. They control a large supply of XRP tokens across the network, making it more like a central bank 2.0 than anything else. If governments decide to start rolling in their own private blockchain solutions, then I believe they'll fail in the long run. It's best for them to create a sort of sidechain or simply a token within an existing public blockchain network in order to increase security and reliability. But that's a decision governments would need to make if they're planning to launch a digital currency of their own.
As for a government-backed digital dollar (USD), everything will the depend on the US government itself. We all know how fierce US regulations have been towards the crypto/blockchain industry in general. Many mainstream crypto companies and businesses have flocked from the US into other countries because of this. Even now, the US has been reluctant to accept Facebook's Libra cryptocurrency from becoming a worldwide digital currency. If other countries start rolling in their digital currencies successfully, then the US might be left behind. I'd be surprised if the US announces that it'll launch a digital version of its USD that would make use of Blockchain technology.
How come you skipped Petro? It was first government coin. I believe is like 2 years old. Yes it have big problems with adoption, but that is normal. Specially since there is such hate of Venezuela in some parts of the world.
Of course, how could I forget that? Indeed, Petro was the very first government-backed digital currency ever created. But, it didn't turned out to be successful after all. That's why I didn't mentioned it in the first place, since it never came into light within the mainstream world. It didn't last for long, probably because of pressure from the US and among other factors. Still, I believe that this movement from Venezuela may have encouraged other countries to do the same.
The world's most prominent countries (like China and Russia) have already announced that they'll be launching a digital currency of their own. With Facebook's announcement of Libra, the process of government-backed digital currencies has been accelerated by a long shot. Soon, we'll be able to interact with digital Fiat leaving physical cash as a thing of the past. But I'm concerned that if the US remains behind other countries in launching a digital currency of its own, the USD will be replaced from its status as the reserve currency of the world. The US needs to adopt the latest technologies (especially Blockchain technology) to stay ahead of the game. Just my thoughts