What would Apple's incentive be to do that? Both Apple and Microsoft have too much to lose if a big budget software maker (ie anyone selling stuff over $50) left their platform. Microsoft will never risk driving Electronic Arts into Google's arms, Apple will never risk sacrificing OSX's image as the "platform for creative people" (which would indeed happen if they lost Photoshop and ProTools). The %30 cut of app sales is a blip on both companies' balance sheets.
