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.
You're right and even if there is a Bitcoin halving, the fact that volatility still existed on it. The price will always change from time to time this is beyond from the rest of stablecoin, Bitcoin is somehow unique compared to other cryptocurrency. People will never forget that there is a Bitcoin halving once you are in the market you will know why.