I agree that’s a plausible scenario, and maybe even most likely given the pattern of history. And I understand and appreciate that you’re not hoping or advocating for that outcome, but highlighting its likelihood.
I also agree with your sentiment that the fediverse seems like a game-changer, particularly in the area of free speech.
You’re right that historically there has been one dominant player at a time, and that it is typically in a period of stagnation or complacency when something new comes along to initiate the shift to the next player.
Social networks are great examples of natural monopolies, largely due to the aforementioned network effect. Without a large, diverse user base they tend to become echo chambers.
But you helpfully point out that there are other new players in the market, to the point that a successful reddit may not be necessary to spur competition for the next great thing.