Maybe. Or maybe it will have all disappeared just by companies going out of business, intellectual monopolist asshats suing everyone, governments trying to control things. Hard to say. Yes, once you've published stuff via the internet to the masses it tends to linger "forever", but that really only applies to data other people have at least a little interest in copying and sharing and preserving (whether legally or illegally).

Condier Geocities going offline - yes there was a vast effort to preserve copies of data. Maybe it will stick around forever in torrent form - but a torrent is dependent on seeders still caring enough to seed it.

And Google Plus is already gone, and I'm not sure anyone gave enough fucks to preserve a snapshot of it (including google), unlike geocities, it's just gone.

Same could happen one day to facebook, and facebook, like google plus, would be far harder to crawl than geocities with far more data, and only some stuff is "public", so without an "inside job" raiding the facebook servers themselves you just won't get everything.