Q: Is it safe to upgrade to OS X while having FCP X on my current OS?

Which version of FCP? Which OS version do you have?

That's a very old version of the OS. I've guessing you also have a very early version of FCPX. First you should check that your computer meets at least the minimum specs for the application.

http://www.apple.com/final-cut-pro/specs/

Your projects and events will have to be upgraded to work with the current version, which is considerably different. There were a great many changes in 10.1. Read about them here, especially the upgrade process for projects and events.

http://www.fcpxbook.com/updates/101/101libraries.html

If you can you should finish any current projects before upgrading your system.

The current OS no longer supports that version of the software.

TToo many factors to make a recommendation. Depends on your system capabilities, your other softeare that might need to be upgraded, and where FCP fits in your needs.