Commitment of extension owner
What kind of feature do you want?
The extension owner should have a standardized way to commit himself/herself if
- development is still ongoing (bugfixes and new features)
- security fixes will be made available
- the extension is abandoned
for an extension in respect to each release and/or LTS release of TYPO3.
I assume that the version number of extensions are more or less meaningless to users and I also assume that users don't know and also don't need to know the version scheme of the extension and how it is tied to features, bugfixes, security fixes and against which version of TYPO3 future versions of the extension will be compatible (even the extension owner might not know this).
Therefore, having the commitment against TYPO3 versions should do.
What are the benefits?
Users can see if an extension still receives security fixes for the TYPO3 version the user uses.
On top of that, having such data in place, it would allow to proactively push the announcement to users (either by a subscription (e.g. a mailing list) or by a service such as https://www.t3monitor.de/
Add some use case
Extension owner drops support (including security fixes) for TYPO3 6.2 or 7.6 and wants to communicate that users should upgrade to a newer TYPO3 release to receive future updates.
Currently, extension owners sometimes announce that via extension updates (something like "This will be one of the last updates for TYPO3 6.2 blablabla").