Info regarding v0 support in D7.4.:

Generally, we advise to be explicit about which API version to use and include the path in the request URL to actively control which major version of the API to use.
Version 1 should be used from hence on. The legacy version must not be used for new applications or research. It is only still around to allow either to support legacy applications that can’t be updated to the new version. We can not guarantee that the fallback behaviour will always work in the future, nor that we will be able to support multiple API versions in parallel. It will go away eventually either because we actively shut it down or because it breaks.

@cmil commented:

This sounds like we would still condone using the beta version while it should actually read: DO NOT USE THE BETA VERSION FOR NEW APPLICATIONS OR RESEARCH. It is only still around to allow either adjust legacy applications or to archive them by means of dockerization. It will go away eventually either because we actively shut it down or because it breaks. I still think it would be better to set a clear deadline than to say we don't know when that will be.

(I added this as an issue because the comment in the GDoc will be removed for publication and we could again discuss this at the summit?)