I do think they will come if there is a way to 'allocate' , say rewards, to non-users of the platform ( those who haven't signed up yet ) . So grandma has a reason to post on steemit if she knows her rewards are being allocated to Johnny her grandson who hasn't signed up yet. Johnny signs up to say hi to Grandma and Grandma knows she is support Johnny's college fund by giving him updates. It doesn't have to show anything about payments at that point as that is between Grandma and Johnny only thus giving the platform a look of just 'connecting' all the time and not 'rewards' all the time.
There are numerous ways this can be used. A sort of 'path' re-direction use cases for SteemIt.