As early as 2020…
The shift would also allow Cupertino, California-based Apple to more quickly bring new features to all of its products and differentiate them from the competition. Using its own main chips would make Apple the only major PC maker to use its own processors. Dell Technologies Inc., HP Inc., Lenovo Group Ltd., and Asustek Computer Inc. use Intel chips.
By using its own chips, Apple would be able to more tightly integrate new hardware and software, potentially resulting in systems with better battery life – similar to iPads, which use Apple chips.
Might be good in the long-term, but I fully expect a bag of hurt in the short term last time they did this it took quite some time for apps to catch up.