No, almost assuredly not. Metal isn't a magical save-all and would require actually implementing a native macOS FFXIV client which is not what Square Enix did. The Mac client is actually just the Windows client, directx calls and exe files and all, with a slightly customized Wine wrapper. A lot of the time, you can even squeeze better performance from stock Wine compiled for Mac than you can using the actual Mac client, but that can lead to some weird licensing issues, as many Linux users can attest.

The closest thing to Metal support you might see is if MoltenVK (the Vulkan to Metal compatibility layer) gets support from DXVK (the DirectX to Vulkan compatibility layer/addon for Wine). So you'd effectively then have DirectX -> Vulkan -> Metal calls being made. (Which could very well still be more performant than Apple's increasingly bad OpenGL support and lack of native Vulkan support).

But at the end of the day, the amount of Mac-only users will not justify the costs of a native client, which is the root of the problem. You're probably better off using Bootcamp if you can or dual-booting to Linux to use Wine + DXVK or Steam's Proton wrapper (which itself is also just a fork of Wine and other things) to play the game than to use macOS.