Ability for apps to talk to each other
This is likely (read: hopefully) the major change coming to iOS 8.
This would lead to:
Sending an image from any app, to any app
(this includes communications apps, photo editing apps, social media apps, etc)
Sending audio from any app to any app
(opening an MP3 from your email in the music app, anyone?)
Sending addresses to any app
(one word: Waze)
Opening links in any app
(instead of Safari, Chrome. Or even paper).
And the list goes on and on. This would be a nice step forward from the way we're using our phones today.
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To those who will tell me we can already to this, we can't. Not unless a develop builds the functionality into their own app themselves. The only reason picframe can send photos to Instagram is because they wrote the app to do so. With native ability to "open in..." you'd be able so send that same message to: mail, mailbox, gmail, messages, facebook messenger, facebook, paper, iphoto, adobe photoshop express, or anything else in the app store that can open images from your camera roll.