So far, the only reasons I've seen people switch from 1 communication app to another, be it for gaming or just day-to-day messaging is either better features/better quality or what they've been using so far turned into shit. And once enough people switch to the new better thing, the rest will follow.
Unfortunately the open source alternative cannot offer either, it's why they rarely succed.
When whatsapp first started to gain traction it was vastly superior to sms, mms was never really a big thing here.
Discord became king because Microsoft bought skype and made it shit and teamspeak/mumble were not as conveniant.
So next open source thing will have to be at least as good as discord and discord has to become really shitty before anything changes. So far, discord has been anything but flawless, but ads are the first step of the enshitification. People will likely switch to web client + adblock. And when discord decides to block that, that's when the first massive wave of people will switch to the new big thing and probably never look back.
I am hopeful the next thing will be something open, I am very much into that, I always try to look for alternatives, but average person doesn't care, so I wouldn't hold my breath.