Bigger than Facebook is a bit overkill lol. They have over 2 billion monthly users. Let that sink in for a moment. But yes clearly it can have some nice growth the upcoming years. But it won't grow faster than what Facebook did. Because Facebook had lots of outside money that flowed in. Don't see the same happening with Steemit.

You also forget to mention the VESTS that we own! Steem Power surely is a part of Steemit as well as Steem Dollar. But is Steem really a big part? People usually just hold it and doesn't seem to affect the community that much. YouTube is also a massive lion that Steemit will never be bigger than lol. The Google guys got so much money behind and could easily start their own blockchain and implement it into YouTube. Let's hope it happens!