'active users' is the key here. I think we'll see the usage of facebook fall, but people will stick to it because they still use it for friends and family. Any shift will be gradual unless more negative triggers for fb happen.
And this may give fb time to adjust itself in some ways for the crypto-powered world over time (however, they can't exactly alter their very infrastructure!)

Steemit is quite a unique space right now, it's quite a different type of content. If it tries to be more profile-based, it could lose its identity right now as a content creation vehicle. (But that's not stopping other projects that focus on the profile /photo , plugging into the Steem blockchain.)

There's room for both? But with token-based platforms on the rise, FB will have to ride that train, before so many others start taking off. Heard of Mithril yet? Narrative?