It's all going to come down to user experience and versatility. Apple is doing some crazy stuff with the M1, but I personally would chock (most of it) it up more to being clever than true innovation. I think only Intel needs to be concerned right now because they're being outpaced by both AMD and Apple. Additionally if the acquisition of Arm by Nvidia results in what people expect, Intel will basically be losing out in every market.

Going back to versatility, there's no way that AWS or Azure is going to move to Apple silicon for their infrastructure, so there's still a massive market for AMD or other Arm manufacturers to target. For the consumer side unless Apple releases a chip that results in them making a sub-$800 laptop, they're just simply not going to capture a large market. With the rise of devices like Chromebooks in education and home there's still something to be said for Apple devices just being too expensive.

In general, Apple devices also leave a LOT to be desired for any sort of large scale enterprise organization. Unless they go back to their 90's and early 00's mindset, I just can't see this changing.

It's certainly exciting to see the CPU market being upended by Apple and AMD, as well as the potential future for a large architecture shift, but I don't think there's any real threat to market shares as a whole.