it's a possibility. but with partners like paypal and coinbase I think they will make much easier for new users start buying crypto.
They target a much larger user base compared to the number of crypto traders.
They have large fan base already when you talk fb alone. So what they can do is how to attract those users to use their coin. There will be hesitations at first because most of them have no idea how to use crypto. But later on, once everybody is using it within their platform, adoption will come easy. But we are all speculating things here. And Libra is not even listed in the market.