[apk-d]

The developers of Signal and similar privacy-oriented apps will probably rather shut down than compromise the security of the app. As long as at least one secure app remains, the policy is pointless. And even then there's other ways to communicate securely. There's no viable way to enforce this.

[angry_octet]

OWS probably wouldn't comply, but have you noticed how hard it is to install something Apple/Google don't want on their platform? Side loading is feasible but improbable on Android, totally impractical on iOS. In place of well engineered solutions from principled developers there would be apps from collaborators. I'm thinking WhatsApp/Facebook will fold pretty soon. 99% of users won't care, and we'll be back to where we were with PGP: most messages are in the clear, the only encrypted ones are huge red flags for further tracking.