Why in the world are you cautiously optimistic? What would give you the idea that meta would do anything but what's in their shareholder's interest. My biggest question is, do we know if activitypub is secure enough to keep them out of its software?

Though this is more federation with a wheel and spoke model than true decentralization where each pier communicates with other piers directly. Each have their place for sure, but they cannot be interchanged because they are not the same thing.