State a policy regarding deprecation of old spec/API versions on matrix.org servers

Hi,

It would be helpful for client authors if the Matrix organization (i.e. the one that runs the official `matrix.org` servers) were to state a policy about whether and when old spec/API versions will be deprecated.

I'm an author of a small client that I worked on in spare time, and it hasn't been practical for me to keep up with the new spec versions in the last couple of years. Sometimes I think about whether it would be worth it to try to write support for newer versions of the spec. My concern is how long my work would remain usable. If I knew that it would continue working on the official Matrix server, I'd be more motivated to work on it. But since Matrix doesn't seem to have a stated policy about this, I feel like I could wake up one day to an announcement that r0.X.Y will be dropped by `matrix.org` servers in a few months, and that my client would then stop working. Were that the case, I'm not sure whether my work would be worth the time.

To be clear, I don't mean this as a complaint or a demand. I don't necessarily expect old spec versions to be supported indefinitely, even though it would be good to support them as long as possible to ensure that clients continue working. And I don't expect that exceptions to a policy would never arise.

What I'm asking for is some kind of a stated policy about intentions, something like, "To the extent possible, we intend to support each version of the client-server spec for X years on the official matrix.org servers." That would be very helpful for authors of client software who want to plan long-term.

(I searched the official spec for "deprecat" and found no results. I also searched the list of open and closed issues for related terms and didn't find an issue about this, so it seems reasonable to open a new one.)

Thanks for your work.

Start by reviewing the official Matrix spec and the open and closed issues mentioned in the report. Determine whether matrix.org can state a support and deprecation policy for client-server spec/API versions; done means publishing a clear policy with intended support duration and treatment of exceptions.

Written by the indexing model from the issue text.