A new player has to come along AND offer a superior developer experience, otherwise there's no incentive for them to leave Apple or Google.
Sure, the freedom tech devs obviously hate the ID thing, but do most normie developers give a crap? I'm assuming not, esp if that's where their income stream is coming from.
The way to destroy the duopoly is probably to give developers somewhere where they don't have to pay fees for IAP.
Imagine, if you can, a digital currency that doesn't require a middleman. Hmm