As per adobe 6.4 documentation, tags should be moved from etc/tags to content/cq:tags. Administering Tags
We have multiple tenants in the same AEM instance, and each of these have separate namespace under etc tags. We are not able to move tags specific to a tenant from etc/tags to /content/cq:tags. Is this an expected behavior ? should we move all the tags under etc at the same time ?
Thanks Jaideep. So the tenant we are currently working on uses classic UI and as part of 6.4 upgrade we are working on restructuring the tags from etc/tags to /content/cq:tags. Since the tenant uses classic UI the tags are getting created under etc/tags.
As per my understanding, all the tags regardless of namespace should be moved under "/content". Any specific reason you want to move one tenant at a time?
Also, as mentioned at  The Tag Manager API supports both the legacy and the new location. When the JCR Tag Manager Factory OSGi Component starts, it detects if it is running on an upgraded instance or a legacy one, and uses the appropriate location.
In other words, if there are still nodes under "etc/tags" AEM will still use legacy location.
These steps work when I move the complete set off tags from etc/tags. If I move only tenant specific tags, any new tags created for this namespace are still getting created under etc/tags. You can check this on vanilla AEM instance.