Personally I don't think Steemit will replace Facebook, and that's ok. Let Facebook be the photo album/gossip platform that it is. There is little to no useful content on that website and eventually people will get tired of the vanity affair that it has become.
I believe you are dead on when you say that once people realize that Steemit exist they will migrate in droves. My goal is to have this be not only a social platform based around niche communities that support and encourage one another, but also the place for people to get high-quality, original content. From news to art to DIY projects; let this be the HUB!
Good point, I agree with you