By "Mobile" you are referring to phones and some tablets. I consider mobile to also be the Macbook Air which is causing a lot of buzz. Could they have thrown in an ARM processor? Yes Apple has the money to rewrite code. Would the Air with an arm processor last for days in the current configuration? Yes. Would it sell? Sure, anything bright and shiny that says Apple would find some market.
But it wouldn't sell like it does with an Intel i5 and i7 Sandy Bridge processor. Performance matters, ARM isn't there yet.