Another possibility is that a new set of bespoke messaging service providers emerges. We may already know several of these, or at least the contenders: Google, Facebook, Twitter, Microsoft, Apple, Samsung.
A set of protocol- and api-based multimedia messaging protocols with centralised directories and abuse controls ... might ... arguably be better than what we have today. Though it's unlikely the contenders will play nice with each other, or spare the plebes.
This happened before.
Generalistic and moderated instance.