It's just a matter of time. Once celebrities really begin to understand the level to which they can monetise themselves with platforms like Steemit, and probably other dApps that will be appearing on the Steem blockchain, there will be a mad rush of them signing up.

Personally I think Steem is going to go up so much it's going to shock the whole crypto world. Look at the volume now, it's practically nonexistent. Steem has the most transactions per day than any other cryptocurrency, and nearly 75% of all Steem is locked up in Steem Power. When the volume picks up it'll go up at warp speed!