Maybe. But, it's said that some altcoins will still exist even after the success of Bitcoin's Lightning Network. After all, XRP being a centralized cryptocurrency, has performed 10x better than most altcoins without the need of the Lightning Network. Transactions are dirt cheap, and fees are ridiculously low thanks to the consensus algorithm used by XRP. Of course, both Libra and XRP will have their distinct purposes within the mainstream world. One will be used as a stablecoin, greatly mimicking the US Dollar, while the other will be used as a means to facilitate payments between Banks worldwide.

Whenever Libra launches by 2020 or not, it's yet to be seen. But if it becomes a reality, it would need to face some stiff competition especially from centralized cryptocurrencies and traditional payment processors. Given that XRP has a lot of Bank partnerships, and an already established user-base, it'll be hard to outpace it. Despite this, I believe that both cryptocurrencies will head their separate ways as they'll be used for unique purposes in life.

Nonetheless, we can only compare Libra vs XRP directly once Facebook's digital currency becomes a reality. Only then, we can measure TPS and the level of user adoption among both cryptocurrencies, in order to determine which is best from the other. Even so, Libra will be completely different from XRP because it'll look more like a real US Dollar (USD) instead of a cryptocurrency. Just my thoughts