Apple's latest iPad processors are competitive with low-end laptop x86 processors. And they have a much stricter power budget than a laptop. If Apple wants to go this route, then they probably have the capability to build the chips to support it.
To really see the benefit of changing they would need to add a lot of cores, and then cross their fingers that 3rd party app developers know how to do true multi-core development.
If that team were to design a bigger core aimed at laptops, then I wouldn't be surprised if they could make it competitive.