It has already started :) I'd say around 60% of major instances block exploding-heads, burggit and/or lemmygrad. Lemmygrad and EH in turn defederate a shitton of instances as well due to ideological reasons. Most "civility" or "law" related instances block piracy instances. The dbzer0 piracy instance blocks anything seen as too right-wingy cuz the owner is an anarchocommunist or something. LGBT instances are blocking & promoting for other instances to block instances that aren't too friendly to LGBT or are simply not moderating or even promoting homophobia & related topics. I actually made a tool called federation-checker.vercel.app/ that checks where an instance stands in the federation "war", so I know what instances to register onto if I wanna see some content that has been blocked by the instances I'm on.