I can't see other reason for Facebook to be raising money if its not to back its own decentralized crypto. FB wouldn't need to raise to issue a stablecoin. Everybody in the original topic said FBCoin couldn't replace bitcoin. While I agree that the ultimate store of value will remain BTC, I think FBCoin could easily surpass BTC in daily usage and, therefore, market cap.
This issue has been on the agenda for a long time, but as far as I know there is no official statement from Facebook! Just a gossip until this official release comes.