Considering the rapid rise of dTube and the coming SMTs I think Steemit will remain a minor part of the Steem blockchain. That's not necessarily a bad thing, and doesn't prevent anyone from continuing to use it to generate a stake of Steem and SBD. The implementation of other platforms and tokens on the blockchain will also allow Steem holders additional opportunities in how to use their Steem.
So, I don't think Steemit is going away, but it also might not remain the largest user of the Steem network for very long.