A changelog is for sure necessary.
Users can’t keep track of all running forum posts.
Having an idea of new functionality without needing to scan through all documentation is ideal.
Also having a change log gives people with DTAP environments for Elasticsearch an idea of stuff that requires additional focus in acceptance testing.
Not all versions are always deployed so you need to be able to read back previous changes.
For us a email notification would be great, I marked the checkbox on downloading 10 times now. But never received a notification, I just scan the download page every now and then.
A forum post could be useful for some people as well. There are few things to keep in mind:
People should not post questions, complaints or issues on this post.
Potentially the forum post drops of the main page quite quickly.
A potential 4th additional option would be to have a json (or something like that) file available so that we people can include a verification in automated setups if they are running the latest version or not.
I would not necessarily include this in Kibana on Elasticsearch itself as there are off course environments without internet access.
Primarily I would say:
Email notification + a clear change log is good enough