Camera and mail apps don't need to be platform-neutral simply because the content and output of those apps are platform-neutral themselves. Mail apps push and pull apps from servers which can be accessed from other outlets/apps. As for camera apps, as long as they are saving a local copy (like Camera roll), other apps will still be able to access those photos. So yes, convenient form of sharing like direct export-from-app may be lost but the real output would still be platform-neutral.