Back in 2013, Apple announced that its iPhone 5S was the first smartphone to support 64-bit applications. This was coming with Apple’s A7 chip, though apps needed to be updated to work on the 64-bit architecture.
App developers at the time either updated their apps or left them as-is. Afterwards, in order for new apps to become available on the App Store, 64-bit code was a requirement once February 2015 came around. This means that some of the older apps in the App Store portfolio may not be 64-bit, and are running in 32-bit emulation.
A pop up message seen in the latest version of the iOS 10.3 beta reads: “This app will not work with future version of iOS. The developer of this app needs to update it to improve its compatibility.” This message pops up when trying to open a 32-bit app.
Apple is likely to reserve a change this significant for a major update: iOS 11. What this means for older-generation devices like the iPhone 5 and iPhone 5C is that they likely won’t be updated to iOS 11. A logical step, since iOS 10 did not arrive for the iPhone 4S. The iPhone 5 and 5C are the next phones in line for firmware obseletion.
Apple keeps backlogs of older version of applications on the App Store for those who may need to use a legacy device. When the user gets notifications from apps for services that will no longer work on older versions, I’ll be time to upgrade.