Tldr: low quality but unlimited storage is expensive, so it will go away in June. However everything uploaded before will not use space for some time. High quality storage has never been unlimited so no changes. A Google Photos storage policy update I would love to read is some guarantee that I can download a backup of my photos if my Google account gets blocked for some reasons.
This doesn't exist. But you can schedule a year of e.g. 2 monthly incremental takeouts at takeout.google.com and stop-limit your dataloss scenario to a window.
btw: I think it should exist. I think google should clarify its 'we terminated you' process to include the takeout function for export of the data they currently hold hostage.