Then I'm going back to Facebook! ...Just kidding!
In all seriousness, I haven't thought about that. My gut feeling is that it won't happen. This is conspiratorial, mind you, and I have ZERO evidence to back this up, but...FB is run by elitist goons, Mark Zuckerberg is the front face of a nefarious organization. I highly doubt that FB would want anything to do with proliferating blockchain technology, which is not really "controllable," per say.
Okay, there you have it! Hopefully, you don't think I'm totally nuts :)
You're not nuts!!
But I think there is a good chance that FB will eventually want to compete, especially if lots of people stop using their site. I can only hope that it would be a 'Microsoft' type situation where they react to the threat (Apple) far to late in the day.
I'm probably just being pessimistic!!
My gut also tells me that they're too late if that's the case; I think there's another Steemit competitor named Yours.org, or something to that effect, but it hasn't panned out yet. Obviously, FB is a ginormous entity, but it's hard to duplicate the kind of explosive synergy that Steemit has, irrespective of the money.