Here's my (uninformed) guess about how this could go. There's already have a fairly powerful ARM chip in all Apple computers - the T2 chip. Assuming it's a si

Here's my (uninformed) guess about how this could go. There's already have a fairly powerful ARM chip in all Apple computers - the T2 chip. Assuming it's a similar spec to the iPad Pro's A12 then Apple could start by moving the OS to the T2 chip, which should improve the battery life of all recent macs. They'll come up with a fancy marketing term for apps that have been compiled for ARM and advertise them as having improved performance and battery life, thereby putting pressure on developers to update. The X86's will initially be removed from all non-pro devices and replaced with more powerful ARM chips, and once there's enough momentum and support they'll also be removed from the pro devices in a year or two.