Keep... using it? How are they going to enforce this?

Worst case scenario, and they somehow manage to remove access to every encrypted chat application in every store (including f-droid) and every repos of every distribution everywhere; and shut down every server in my country; and get telecoms to block every port of every secure chat client; I've got VPSes outside my country, and VPN configured. I'd probably build my own encrypted chat - centralized server hosted on my VPS - with PK E2E encryption.

For a big, public chat app, the bar is higher. For my family and friends, something I hacked together would be good enough. As long as encryption is done in the client, hiding metadata (who's talking to who) isn't important for my use (we're all family & friends). Chat is the most trivial of applications to build; it only starts getting complex when you want it to be serverless, or anonymous, or have PFS. Securing popular servers (attractive targets) makes things harder; being popular makes things harder.