Yes, that would be a possible evolution of permissions. If an app lets you choose a picture from your photo library, iOS swaps you to your camera roll where you

Yes, that would be a possible evolution of permissions. If an app lets you choose a picture from your photo library, iOS swaps you to your camera roll where you select the image and then click "Share this image with app". You then get redirected back to the app and iOS sends the app only that image. Currently, for things like camera, microphone, location, etc. you can always revoke that permission after granting it via Settings.