Libra is expected to be launched by mid-2020, if everything goes as per their plan. But the problem is that not "everything" is going as per their plan. Last month, the Senate Banking Committee conducted a hearing on Libracoin. And from what I have heard, the response was mostly negative, as well as hostile. A number of senators, including Brian Schatz, Kyrsten Sinema, Pat Toomey and Chris Van Hollen participated in the hearing, with the most hostile reaction coming from Van Hollen. Schatz indirectly said that given the recent issues faced by FB (especially those related to data-privacy and election-meddling), they should not be taking the lead on a cryptocurrency project.
Unfortunately, things will not be so easy for Facebook to launch Libra as promised by 2020. We've already seen many governments opposing the same, especially the US. Since Facebook's homeland country is the US, it needs to strictly follow its regulations if it wants to have a successful launch in the future. Then, it could comply with regulations from other countries worldwide as it expands its operations. But, knowing that central banks have been in power for quite some time, it'll be nearly impossible to launch a worldwide digital currency by its own.
The biggest disadvantage of Facebook's Libra cryptocurrency would be its full transparency towards the company itself and worldwide governments. Considering that Facebook has been a threat to people's privacy, it could very well obtain sensitive information among transactions performed within the Libra blockchain. In effect, people would lack the ability to control their own money (contrary to Bitcoin and other decentralized cryptocurrencies) greatly defeating the purpose of a Blockchain. Which is why, I don't see Libra going anywhere even after its launch within the mainstream world.
Nonetheless, Facebook's cryptocurrency may only be a dream as it wouldn't be able to launch in the future because of oppressive governments worldwide. They believe that Libra will replace existing Fiat currencies as people will tend to use it more than anything else. Since governments want to maintain control of the monetary system, they won't allow this to happen anytime soon. In the bright side, Bitcoin and other decentralized cryptocurrencies will continue to function as intended for a very long time no matter what happens with Libra. Just my thoughts