Older project files can be opened (usually) by newer versions of the apps. Yes, you should be able to open that file with the newer app version. BUT, if you need to make changes to that template, do it in the older version of Motion, then copy to the newer version of FCP. You can go old to new, but not new to old backwards.
There are some templates, if they're old enough, will need to be updated in Motion itself. But copy it over and see what happens.