I think this is kinda technically a win for Beeper. I would've expected another 100% lockout to be Apple's priority. They were instead only able to block 5%, which sounds like a heuristic being applied, and possibly not even an intentional block of Beeper (in the sense that some anti-spam service may be identifying some Beeper users).
They can certainly escalate with protocol changes, but they still have to contend with older Macs, iPhones and iPads which are out of the support window losing access-- so if they want to update the protocol they either have to issue out of band patches for these devices or cut them off too.
This is assuming you can actually iMessage on iDevices that are out of software support -- maybe our iOS friends can let us know.
They can certainly escalate with protocol changes, but they still have to contend with older Macs, iPhones and iPads which are out of the support window losing access-- so if they want to update the protocol they either have to issue out of band patches for these devices or cut them off too.
This is assuming you can actually iMessage on iDevices that are out of software support -- maybe our iOS friends can let us know.
EDIT: This take seems more plausible (that this is intentional by Apple): https://news.ycombinator.com/item?id=38648030