The reason Final Cut Pro has been languishing without a new update is that Apple is doing more than just creating a new version for Intel devices and Apple-Silicon devices.
Apple is creating a whole ECOSYSTEM for all their devices to run from iCloud proxy workflow based version of FCP. A PRO version for large screen devices and a lite iCloud version for iPhones and will rely on AMX architecture in the A11, A12 and A13 chips, Neural Engine to do incredibly powerful things even on your iPhone 8 & up. This ECOSYSTEM will help Apple grow an ever larger group of new budding editors to the platform.
(This is what I logically think is the natural progression of the Final Cut environment should be.)