Tim Cook said Apple has been working on products in new categories. I wonder if A-chip based laptops would be constitute a new category. It may or may not be, depending on how one defines a category.
If Apple were to produce A-chip based laptops, it will also make MacPro with A-chips. This way, there is no fragmentation in the OSX platform. It's a big effort. But, if there is only 1 company in the world that can do it, it is probably Apple.