I think there are at least 2 or 3 positive feedback loops that are really just getting started. Hard Fork 19 changes the game. For those who haven't read, Hard Fork 20 looks to also be very interesting: https://steemit.com/steemit/@steemitblog/proposing-hardfork-0-20-0-velocity.

There's no doubt in my mind that Steemit will have over 1 million active users within a couple of years. Demographic is an unknown for me, but as long as there are users all across the world, it's bound to do very well.