I would like to play devil's advocate
From this article I read
Unlike the volatility seen around other cryptocurrencys in the past, we believe that Libras focus on creating a stable, low inflation currency backed by a reserve or real assets is a differentiator. Further, unlike other stablecoins, Libra will not be pegged to one currency but instead a basket of assets ranging from bank deposits to short-term government securities.
https://www.cnbc.com/2019/06/18/the-difference-between-bitcoin-and-facebooks-libra.htmlWill Libra Coin bring Down Bitcoin's dominance in the market, your thought?
It is stated already that it is a stable coin so there is a very low chance that it can dominate the bitcoin in the near future if in case it will be launch. Even if Libra will not be pegged to one currency, they still need more than that to bring down the King of crypto currencies.