Corporations have a drive to increase profits, often to a suicidal level, so no matter what I expect reddit and discord to not be around forever and even when they aren't killing themselves I expect them to abuse my rights and privacy at every opportunity.
Federated technology seems cool but ultimately no one uses it and even when people use it the inherent interconnected nature of it turns it into twitter but even fucking worse. Bots, scammers, probably state backed propagandists, etc, all roam almost unchecked and sometimes even flood the fediverse with spam. Creating communities and cultures is almost totally impossible as everyone gets a little bit of everything all of the time.
Forums like this one ran by individuals and small groups have been around for decades covering countless topics and given how shit the internet is becoming I expect them to remain important for the foreseeable future.