1. crypto currencies and P2P payments
2. Take clues from Steemit (a decentralized social platform that runs on blockchain) and how they utilize blockchain
3. Use to combat censorship in countries that are not favorable to Facebook
4. Use BC to combat fake news
5. AI platforms
6. Streaming services
Just because they have a centralized service doesn't mean they can use some of their considerable capital and branch out into other areas and offerings. To think FB will always be a social media platform is kind of. . .myopic wouldn't you say?