My perception is that this is zero sum game. For big companies like Apple their capitalization makret is driven mostly by institutional and megafunds money. Those guys are very inertial in their invetsment strategies, and their ammount of funds is stable.
Decrease in Apple demand should mean that those guys realocated their funding to other IT companies, or moved money to another industry (this is less probable and takes more time).
In a hypothetical scenario, would you rather own all of Apple or all of Google, Exxon Mobil, and Caterpillar?
My point is, I'm not sure P/E means as much with such a ridiculously high market cap.