[asciimike]

On the first, I've worked as a PM on Firebase, App Engine, and Endpoints.

Nobody has been forced to migrate from the Firebase RTDB to Firestore (and AFAICT the Firestore API hasn't deprecated anything?), App Engine deprecations (https://cloud.google.com/appengine/docs/deprecations) are basically "you can't do new things using these old things, but the old ones will continue to run" (though other deprecations I've done have provided clear explanations of why we're deprecating and how someone can work around it), and Endpoints is still around despite being comically out of date (it's even getting a managed version!).