I think that Facebook is no longer as famous as before, now is more Instagram, Twitter is still among the best, Whatsapp, but everything depends on the trend of the public and also mobile applications.
The problem I see is that once published in a blockchain, it will never be deleted and it is necessary that a social network also has the opportunity to delete its content.
I suppose that in the near future social networks will use the blockchain only as a means of reward.
Thanks for sharing 
Hello my dear @jadams2k18, welcome to the debate brother.
Of course, there are many applications that facilitate the use of these networks and make them more attractive and efficient, there is a big gap between these networks and those based on blockchain
Well the rewards are what are bringing more users to blockchain, the idea of creating and being rewarded for it is very attractive.
Thank you brother for your great comment, all my respect for you