>the waves of people leaving anything are always overblown

Digg, MySpace and Vine?

Old world decay model, new world is twitter or facebook. Mass user exodus to a point a platform is a genuine wasteland, this means bots get deployed to prop up metrics. The money doesn't come from users, but the beleif of access to them via a platform. As long as there is a appearance of consumer data/attention you can access, then everything is fine re: revenue. Dunno how discord will fudge things though, since discord doesn't quite (historically) fit traditional social media models so maybe you'll be right in the end.