In my opinion, there is no need to document the changes in a way that is both backwards and forwards compatible. django-mssql, at least, does not attempt to support multiple versions of Django. I believe try to support multiple versions of Django would be more effort than it's worth (after all, we don't have this required for any backends in core), but maybe there are backends out there that attempt to do so. I have created a thread on django-developers to get feedback on this question and more, so that we have some guidance on what documentation to add. Since we haven't been documenting as we go this time, I believe the most efficient way to add this documentation will be to do so in a reactive fashion (to reported breakages in third-party backends) rather than trying to anticipate what parts of the API developers are using.