The real fact on the ground is that bitcoin would continue to fluctuate despite the many speculations. Beyond 2020 and the successful implementation of Libra as a cryptocurrency that is attached to a popular brand as good as Facebook inc, bitcoin and all other cryptocurrencies would be affected by price volatility.
Bitcoin and the whole cryptocurrency scene are already being posted and ads containing info and coins are already spread in facebook way before Libra is made and published. So I don't think that the Launch and successful implementation of Libra will really affect bitcoin despite how big the company behind it because facebook is already promoting crypto/bitcoin a long time ago.