I expect It all hinges on the price of advertising space as that's how it's funded. Social media in it's own entity is a very profitable business the facebook ad space alone is a diamond mine so Mr Zuckerberg can afford to dish out a few cents a post of that I have no doubt.
Is Steemit trying to attract the general audience of Facebook is another question & the reverse of the same question is even more important, Is Facebook trying to attract the general audience of Steemit?
I don't think it is or it can, Steemit is a site for authors, journalists, Artists & photographers to socialize with each other on the internet. Facebook aren't going to pull us out they aren't of our ilk & eloquence. The average Facebook user wouldn't last 2 weeks on here it's a different ballgame.
We want new users but we want good ones & that's what we will get the bad ones can fall by the wayside & go & spam up twitface.
Comparing facebook to Steemit is like comparing a Ford to a Bentley, they are both cars, they will both get you there, it's just that one is a more refined & pleasurable experience.