One thing I've noted is that online forums have expanded and consolidated a few times over the decades. We saw expansion to start, back with BBSes, then consolidation to FidoNet, Usenet, and services like AOL. Web forums took us into expansion. Link aggregators and meme sites moved toward some consolidation. Reddit is basically Usenet 2.0.

I suspect we may see another round of forum expansion again as people want to carve out their own niche communities again. We might not see Usenet 3.0 for a bit while we let people expand then let a new site come along and consolidate.