In the long term, simple social apps will not be posting all their posts because it would be too expensive to do so.

In the short term, while the HIVE price is low, people will enjoy it, but later the blockspace will be reserved for usecases which generate more money than a random post.

Not sure what those usecases are, probably custom_JSONs of games with very highly valued assets or controversial posts which the author knows will probably be censored if not paid for in RC to post on hive.