It is an important question, but Google services which are largely consumer-based and no cost are a very different world from Google Cloud. People get a lot of Internet Cool Guy points these days from falsely conflating the two.
I'm not the to make commitments but our history has been solid, and our deprecation policy is embedded in our terms of service for every Cloud user.
The only product I can remember us deprecating in GCP was Prediction API in favor of the much-preferred Cloud Machine Learning Engine, and with that came communication to every single affected admin and a _year_ before cut-off.