I've been wondering if we can already see the foreshadows of Apple's next move, actually: CKV is already only possible between modern (iOS 17.2 or macOS 14.2 and above only) devices, and their RCS implementation will presumably not be end-to-end encrypted.
I could see them opening up "legacy iMessage" (i.e. non-CKV, non-ephermerally-encrypted) and integrating RCS, but assigning new color to "modern iMessage" exclusively. That would credibly count as opening up their service, while still preserving a distinguishing feature for Apple devices, and even nudging people to upgrade some old devices.
As much as I would like to see Apple, Google, Amazon, Microsoft and the like not have so much power (socially, economically, most likely at the government level as well), I think the only way we'll actually make any progress towards the problems that allow large companies like that and allow their negative consequences is to attack some of the specific aspects of our current system they abuse to their benefit, and not them specifically.
For example, very strict privacy laws and control over tracking to curtail the biggest problems of the data companies, laws about control over your own devices and what you do on them (software) and with them (repair) for the hardware companies, etc. Otherwise we'll just see some other company take up the same practice and have all the same problems.
Because it would be the most sure-fire way to be certain that it actually gets done, whereas "the market" is less certain and prone to manipulation tactics such as lock-in. Returning to my original question that you kind of dodged, why not let them intervene?