According to an update on Apple’s Developer site, all new apps uploaded to the App Store starting in February must support iOS 8 and use 64-bit code.
Here is what apple says
Starting February 1, 2015, new iOS apps uploaded to the App Store must include 64-bit support and be built with the iOS 8 SDK, included in Xcode 6 or later. To enable 64-bit in your project, we recommend using the default Xcode build setting of “Standard architectures” to build a single binary with both 32-bit and 64-bit code.
Writing against iOS’ most current SDK is nothing new, as the company made similar demands for the iOS 7 SDK. What is new, however, is the requirement for 64-bit support.
Currently, developers have the option to submit 32-bit apps, but after February 1, they will have to include 64-bit support for any new apps they submit. Developers do not need to add 64-bit support to existing apps, unless they are submitting an update after February 1.
Adding 64-bit support to an app usually doesn’t take too much time. Developers will have to use the most recent tools as Apple points out that the app should be built with the iOS 8 SDK. Notably, Apple will not be able to drop 32-bit support until iOS devices running on 32-bit processors are left out of the iOS update cycle
For iPhone owners with 32-bit devices, the rules will hopefully mean nothing. But those with 64-bit devices could see significant improvements in their apps’ performance. developers have had thirteen months to go 64-bit — months during which they also needed adjust to iOS 7’s new design, iOS 8’s new APIs and extensions, and the new screen sizes of the iPhone 6 and iPhone 6 Plus. Apple’s new rules will give them the push to update their apps with 64-bit support, mostly to the benefit of users with newer iPhones and iPads.