When bitcode is enabled for a target, all the objects, static libraries and user frameworks used when linking that target must contain bitcode. Otherwise, an error or a warning will be issued by the linker. (Note: missing bitcode is currently a warning for iOS, but it will become an error in an upcoming beta release of Xcode 7.) ENABLE_BITCODE should be consistently turned on for all the targets. If you use a library or framework provided by a third party, please contact the vendor for an updated version which contains bitcode."
Dear God, do we need to wait for all libs to update? :S
This is the insane part - you're relying on things you have zero control over and zero support for. Apple's requirement is no different than some fatal bug discovered or backdoor discovered in those libraries - except Apple is giving you some notice without immediately putting the liability on you.
Is there a fundamental change of architecture planned for future iOS devices?
My guess is that it is future-proofing towards running iOS apps on Mac OS and/or running (parts of) iOS apps on the Apple Watch. It also might mean that Apple plans to make their own ARM extensions (for example, I suspect having the CPU know about tagged pointers, so that an 'add' instruction can do an indirection, if needed, might be an overall win)
Update: the release notes for the Xcode 7 Beta say:
"• Bitcode. Archive for upload to the App Store in an intermediate LLVM binary representation that the store can then optimize into the 64 or 32-bit executable to be delivered to customers."
This falls under a feature they call 'App Thinning'. It makes the App Store optimize an app for the device it gets installed on, CPU-wise and asset-wise, and also allows your app to download some resources on demand.
Oh boy; if this is the start of apps lazy-loading resources and code, I'm really excited. It's the largest barrier to signing in your account from any device.
What would be the selling points for an ARM MAC? Access to the iOS app store software library? (unlikely) Better battery usage? (maybe) Super cheap devices? (un-apple-like)
Changing archs has been done before but I don't see a rosetta for intel apps running smoothly on arm. Virtualizing windows and linux is another killer app for intel macs that would be missed for some.
Perhaps it's also a shot in front of Intel's bow.