I think the email comparison is apt. We are currently in the bbs/dial-up ISP stage of the fediverse. When people had aol.com or netcom.com addresses.
That gave way to powerful centralized services such as Hotmail or rocketmail, that had the promise of never changing your email again. We then saw Gmail become the big boy on the block with amazing technology.
Even with these powerful entities, there were still hobbyists and corporate email.
I predict the fediverse will follow a similar path. lemmy.world and beehaw are like the netcoms, or even the bbs's, basically hobbyists, and Internet communists setting things up for the common good, or simply because it's fun.
We're going to see instances fill up, become unstable, unreliable, etc. People will get frustrated when Lemm.ee, or their preferred instance can no longer support the volume they have attracted. We'll see a professional service like a Hotmail that promises a forever home. You'll likely also see vanity instances like what rocketmail offered. Given the nature of the interest based servers, we'll likely see vanity instances come about singer than they did with email: starwars.fedi, lotr.verse, piano.lemmy, etc.
Once corporate interests start to see value in a powerful, stable instance that can collect user data and serve targeted ads (starwars.fedi is easy to target), they will dump enough money to push out the hobbyists. The hobbyists will not go away, but they won't be needed anymore.
That's when you'll see the disruptor. Someone who comes into the space like Google did, and the fediverse will be an open protocol that is dominated by a few massive interests.
All in all, I'm not predicting doom, just the natural course of events, which actually will be great for the fediverse. Just like I love my gmail.com account more than my hotcity.com account, I think the future of the fediverse is bright, even if corporate interests get heavily involved, and dominate the 'verse, because there will always be room for innovations, and hobbyists, and while a single company could dominate, the protocol is still open for anyone to do their own thing, and not be bound to a single company if they don't want to be.