I think the turning point (if it comes) is when celebrities (they don't need to be huge at first) or other successful social media figures start to sign up and endorse it. This will give the platform a lot of prestige and legitimacy, similar to what happened with Reddit and AMAs.
I recently wrote a post on some other possible scenarios in the not so distant future after something like that happens, check it out:
https://steemit.com/steemit/@moonjelly/what-if-steemit-goes-corporate