Apple has been (almost) always using Intel chips for anything other than iPads and iPhones. It is possible though that at some point they will leave Intel and invest in their own processing technologies.
Intel has been making the best consumer processors for the past 10 years. While more expensive than competitors, Apple is all about premium computing, so that was the choice for them. Now Ryzen is a thing, but still Intel and Apple probably have good deals that won’t change anytime soon. And even if that changes, it won’t be for AMD.
Intel also has the best chips for low power, low thermal situations. Most Macs are slim and portable and don’t have huge batteries and/or cooling systems. Therefore it is best for Apple to stick to a core i5 or i7 if it stays cooler than a Ryzen processor. Even if that costs a bit of performance.
The A processors.
Those processors that are usually marketed as A12 or A-something. Those are used in iPhones and iPads. And lately, those have been performing very well. The latest Apple mobile ARM based chip, performs as good as a Macbook. This is because Apple has optimized everything. Since they make everything, phone, chip, software, from scratch, they can build great performing devices. But desktops are a bit more complex, and the ARM chips are not designed with the same philosophy in mind.
In theory they could though, make a chip powerful enough for a thin and light laptop. Maybe a new Macbook. But this means that they have to invest a lot of money for manufacturing larger chips, that consume a bit more power and have probably lower yields. This costs a lot of money. It shouldn’t be a problem for Apple, but they could do something a lot smarter instead.
What they are probably trying to do.
Apple is so big that they could be doing everything at once. They could have teams working on a desktop/laptop CPU similar to the A12 chips while at the same time, having no intention of leaving Intel. They may even have prototype devices ready and even plans for mass production ready to go. But what they would probably want for now, is for such rumours to start going around, putting pressure on Intel to drop prices and get Apple better deals for the processor Apple already buys.
What if Apple really makes a CPU?
They will probably release it on a device like the Macbook. Maybe that’s why they released this product. It is so thin it doesn’t really make sense. It is weak, and has one port only. At the same time is very expensive and a terrible deal. So Apple has a well known product, that only a few people care about. Those are probably casual users, that want a small and long lasting computer for mail and internet browsing. The Intel chips inside those Macbooks are so weak that Apple can easily put an A12 in, and say that their chip beats Intels by 70%. Then, they can beta test the architecture, and once it is mature, design bigger chips for Macbook Pro and iMac devices.
What about AMD and graphics.
AMD makes great graphics cards for certain tasks. It has worked really well for Apple until now. But in an A12, the best part is the graphics cores. So, if Apple replaces Intel chips with Apple chips, they will probably make their own graphic processing units too.