I'd argue that the software people run on a Mac Pro is a strict superset of the software people run on a MacBook. Combine that with Apple's philosophy of hiding technical details from users (e.g. with fat-binaries in Darwin), so if Apple _does_ switch to ARM for the MacBooks that's not a problem: Microsoft Office for Mac, Chrome for Mac, and the rest (if they aren't just Electron apps like everything is thesedays) will have to be an x64/ARM fat-binary for the Apple App Store - and no-one will complain about specialty pro-only software distributed outside of the store only being available as x64.