Facebook should probably wait for a few years until it does it. Currently it is the main traffic driver for “news” outlets and they will likely try to discredit the search engine.
Someone else will do it by then. Also, i dont think so - facebook has been better at giving traffic to other sites - unlike google they dont usually scrape and rehost them .
I totally support facebook leveraging their tech and data, all i am saying is that it will be discredited day one given the media hostility against it.