[gds44]

Once upon a time I used to live in libraries to make any kind of progress on certain problems. Then Google arrived and my library visits reduced drastically. Yet libraries still stand. And I still head there whenever I need some peace and quite. Something like that will happen with StackOverflow, Wikipedia, Quora,Reddit and even HN.

[niemandhier]

The difference ist that libraries are vaults of knowledge usually operated by governments to ensure access to the public.

Of all the examples you named only Wikipedia has a mission that is comparable to a library.

All the others will probably perish and exist as datasets you can buy, just like some social networks of yore.