Apple has announced to developers new iOS apps submitted to the App Store must support 64-bit apps starting on February 1, 2015:

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.

iOS apps with 64-bit support must be build using the iOS 8 SDK. The move looks to transition apps towards taking full advantage of Apple’s A7, A8 and A8X chips, which support 64-bit.

Oh, as for the developers out there, don’t forget you’ll still need to support the A5 processor found within the original iPad mini–a chip which debuted with the iPad 2 then made its way to the iPhone 4S back in 2011–for at least a couple more years.