How many users are their currently for Steemit?
How many users are there currently for Bitcoin?
http://www.coindesk.com/2016-bitcoin-challenge-100-million-users/
Apparently there are only 10 million BTC wallets, so actual number of users is even less. The average user might even have 10 wallets. I'm skeptical about putting Steemit over 100,000 by the end of this year for total accounts, even less for active users. Facebook may have 1 billion accounts, but there are many duplicates and nonactive users. True active users of Facebook is probably more like 200 million.

I think Steemit will remain very niche. Multiply current number of users by 3-10 times by the end of the year then continuing that growth rate for 2017. It will be strong community and perhaps become the top discussion platform for cryptocurrencies. Bitcointalk has nearly 1 million members, maybe 10-30% are all that active. I'd call it a win for Steemit if in 2017, Steemit has a higher marginal gain of membership than Bitcointalk.