The -meta packages are maintained; it is just that many members don’t seem to know the actual purpose of them.
They aren’t meant to force you on to the newest kernel; they are meant to stop you from continuing to run an unsupported EOL kernel that has been removed from the repos.
When linux615 is completely removed from Manjaro’s repos, the linux-meta package will be updated to automatically install linux616 and remove the no-longer-available linux615 from the user’s machine.