Integrating the backends of the messaging systems, not the frontends. There will still be separate apps called "Messenger," "Whatsapp," "Instagram," etc., but they'll just be different fixtures set on top of identical plumbing.
... in much the same way that Ford (say) could design one car and then sell it to very different audiences as the Ford Taurus, Mercury Sable, and Lincoln Continental.
I don’t disagree, but there seemed to be a lot of a publicity around a backend tech change, and to me, it is that publicity that undoes the whole idea of keeping businesses separated. As a side example, everyone knows that Coke makes Diet Coke, but many don’t know that they make Sprite. The Sprite model seems to be a better approach than FB’s new Diet Coke approach.
This approach opens up exciting new opportunities for market segmentation via badge engineering: https://en.wikipedia.org/wiki/Badge_engineering
... in much the same way that Ford (say) could design one car and then sell it to very different audiences as the Ford Taurus, Mercury Sable, and Lincoln Continental.