A reply on OP's post states: "... We now generate Auth keys by default for new users (more secure key which didn’t exist when the Gemini API was originally created a few years ago) and will have more to share there soon. ..." So there is something new in that exact area but the details are forthcoming.

I think brand new stuff is probably safe, but old keys that currently being used for AI and non-AI stuff - if Google disables them for AI and it turns out it was actually not being exposed publicly, could disrupt a user's production service relying on AI.

They messed up by allowing old keys to be used for both private and public APIs in the first place, but now it's difficult for them to undo that for existing keys.