Facebook might enter and it will not even be a competition. Libra is something that is backed up by the fiat. If we will be talking about crypto currencies, bitcoin and altcoin will still be the thing. In terms of usage, obviously fiats will be the winner since cryptos still has a little place in this world right now.
Facebook has a lot of obstacles to over come to come up with their coin and if they get the license then people will be flooding into the coin because you can trust them as a stable currency and they will be transparent unlike other stable coins we have right now, fiat still rules the finance sector and you need fiat to invest in bitcoin or any crypto.