I think you can take this even further and ask if any social media platforms will be as big as those of this past (and rather long) period. Reddit, Facebook, Twitter, YouTube. It’s been a very notable period of centralisation of the web from about 2010 or so. And it’s worth wondering whether it was an anomaly.
There’s certainly been some fracturing lately and for good reasons (we were never the customer and the internet has always worked this way with people moving freely).
On the other hand, the idea of having a personal home on the internet, a true avatar and the idea that huge serious things can happen online … both have gone mainstream and probably can’t be put back in the bag.
Against these requirements, an open protocol is an obvious solution, as we’d all tend to agree, but not trivial as corporations still want to make money some how and so may not buy in. Plus getting the protocol right at the right time is non trivial (I personally suspect avtivitypub has not done this and as a result we’re in an awkward position at the moment).