I think Facebook will die a slow death ( if it doesn't adjust ) and any new social network platform that wants to succeed and last will need to reward its content providers. I made a meme awhile back that gives my view on the rise of Steemit vs Facebook or more widely put -- New Social Networks vs Old / Current Social networks.

Here it is :

So to answer your question. No I don't think a social giant like Facebook or reddit will exist but I do think it's possible to have large front runners like Steemit that rewards it's users.