Anyone putting off updating to the current OSX patch may want to look at the list of security issues this patch addresses to decide if it's worth updating or postponing for now. https://support.apple.com/en-us/HT213183

But yes, updating OSX will disable the official FFXIV launcher for mac.

For now I'm holding for an official launcher update until FFXIV patch day (next reset) in hopes it's fixed then, but this is also a personal work computer so I won't be able to delay patching OSX for much longer. :/