While I don't think we'll see Meta do this for their apps, I do expect (if they can stomach the cost) Epic and Valve to build their own stores.
Epic didn't have much success getting Android users to sideload Fortnite, so I don't know how well it will go for either, but I know that gamers are a dedicated bunch and both Valve and Epic want to have the user-level connection.
From what I've seen, one of the requirements of a competing App Marketplace on iOS is that they allow any developer to submit apps to them—I'm unclear on whether they can restrict by category (eg, only allow games), but AIUI they can't just restrict their own marketplace to selling the apps they themselves publish.
This is a very interesting requirement, and will definitely at least make companies like Epic, Valve, and Facebook pause and think before deciding whether they actually want to be running an App Marketplace.
Or even worse, that utility apps that are needed in daily life require their own "store"