When will version 4.1.18+ be available? Version 4.1.18 was released almost a month ago.
Think 4.1 has had it's last security update and version is now un-supported for
any fixes to code or security updates.
4.1.18 (Build: 20250414)
https://moodledev.io/general/releases/4.1/4.1.18
So there is no + for 4.1.18.
Should you update? Probably. Goal might need to be next Long Term Support verison which is 4.5
https://moodledev.io/general/releases/4.5
But before you pull the trigger on that, do server environment check and check your addons to see if they have a compat version for 4.5 and beyond.
If your server is not using Git versioning for core, would be a good time to get your core code under git.
https://docs.moodle.org/500/en/Git_for_Administrators
'SoS', Ken
General support for 4.1 ended in December 2023 per https://moodledev.io/general/releases - it will remain in security support until December 2025
Per your question, there haven't been any changes to that branch since 4.1.18 was released, hence no + version. If you want to see any upcoming changes you can check https://tracker.moodle.org/projects/MDL/versions/19659 (as above, it won't be receiving regular bug fixes)
There have been NO changes to Moodle 4.1 since the release of 4.1.18. If there are no changes then there is no update and no + version. It doesn't make sense to create a + version that is exactly the same as the non + version.
As version 4.1 is nearing "end of life" you would/should only expect urgent security fixes to be added. There haven't been any.