Not sure about Cook's ambitions. If he's been eying for the CEO title and he's not made the successor, he can be easily lured away. Ive on the other hand, I would imagine he's happy where he is now. Ive designed devices are probably getting close to a 1/4 to a billion units sold. I'm not sure if he can have that kind of influence anywhere else, nor his desire to be a CEO. Jobs has to know these points. So unless Ive is more ambitious than Cook, making Ive the CEO won't be playing the cards right.