Hi,
I also have three production servers running and none are on master (5.4), even though I also need some stuff from the master.
I have one for me as active test server that is on master branch.
Mark - FusionPBX announced the release of 5.4 as current. Current master will be moved to 5.5 branch.
I'd wait until the official release (even though he did announce it in June continuing education).
That way you will have all the features you need in stable environment.
As for having master as production. I had one running as such, which I migrated to a current version.
Think that answers your question.