This is a very interesting development. I haven't been able to find whether Apple plans to enter the x86 market or is going the ARM route with their desktop computers, or is planning to develop its own flavour compatible with none of the others. It's also interesting to see whether that'll be the end of Bootcamp.
Exactly. What appears to have leaked is that Apple is planning to stop using Intel, and probably x86.
That doesn't mean they're going to go to ARM.
Not even unifying macOS and iOS means going to ARM. New iOS XCode projects have defaulted to compiling to llvm IR and being uploaded to the AppStore that way for several years already. You can change them to compile to native aarch64 code, but I'd bet most people don't. With watchOS and tvOS you don't have the choice -- only llvm IR is accepted for upload. I'm expecting Apple to remove the option to upload as ARM code and only accept llvm IR any time now -- last year they forced everything to be 64 bit, so maybe this year it will be forcing everything to be llvm.
At that point they can use any CPU architecture they want. Maybe something they design themselves. Maybe something existing and free such as RISC-V, saving Apple the work of creating all the compilers etc themselves.
Apple has their own existing rather good ARM micro-arcitectures. Better than anyone else's (whether standard ARM or Samsung or Qualcomm), and pushing hard against the lower end i3s and i5s. Changing the instruction decoder on those to use a slightly different (and maybe simpler) RISC instruction set would be a relatively simple task.