the transition to ARM to take at least two years to complete
We know Apple plans to release a 13-inch MacBook Air and 13-inch MacBook Pro with the new chips in the coming months, but other ARM Macs won’t show up until 2021
AppleInsider advises that third-party MacOS app might not work as well (or at all) on ARM Macs — at least at first.
Apple has a good track record of supporting older products well after launch, so its Intel Macs will absolutely remain relevant even after Apple has fully shifted to ARM.