Back around 2009 when Facebook was first becoming ascendant, people wondered if social networks were generational. I.e., would each younger generation be willing to use the same social network as their parents?

I think the de facto surrender of Facebook to TikTok here is evidence that social networks ARE generational. That implies that TikTok may reign supreme for about 20 years, but thereabouts, they'll have to contend with yet another rising challenger.