Your shiny new iPhone is about to get apps that work with it properly. Via the Apple Developer page, we find that starting early next year, all apps must have 64-bit support. Those apps must also be built with the latest Apple developer environment, and utilize the latest iOS SDK. It’s a push toward the future, but not one that should come as a surprise. Apple did the same thing with iOS 7, which was more a push for visual upgrades.
The deadline to update a dated app is February 1. After then, all new apps submitted to the App Store must have 64-bit support, and be built with the iOS 8 SDK. Apple advises all Developers use Xcode 6 default build settings (“Standard Architecture”). That will give a 32 and 64-bit binary.
Why insist on 64-bit? We’re not turning back to 32-bit, and 64-bit allows for better virtual memory allocation as well as continuous memory usage. Those apps that support 64-bit architecture will run faster as a result.
Existing apps will be fine, unless the Developer submits an update. Apple has not announced plans to pull any apps that don’t support 64-bit architecture, and likely won’t until their hardware profile reflects a move away from 32-bit completely. Of their current iPhone lineup, only the iPhone 5C, with an A6 processor (and no coprocessor), is incapable of supporting 64-bit.