iOS 12 will continue supporting iPhone 5S, WebKit developer reports suggest
References to iOS 12, Apple's next iteration of its mobile operating system, have surfaced in development testing reports for WebKit, with the appearance strongly suggesting Apple will be bringing the next major iOS release to the iPhone 5s as the oldest supported iPhone model.

Listings in the bug-reporting section of the open source Webkit project page, discussing API tests for the software, includes a report from one developer in January showing an implementation of the testing suite could be run using Python. The report, spotted by MacGeneration, specifically mentions iOS 12 in multiple sections, as well as the iPhone 5s, including the confirmation "iPhone 5s running iOS 12."
Rather than an unreleased version of the operating system running on an actual iPhone 5s, the start of the report indicates this to be API tests running in a simulator, mimicking the iPhone 5s in software.
If genuine, this would indicate both that iOS 12 is being used in testing of important software, like Safari. It would also make this a sign that iPhone 5s users could still be able to use the next iteration of iOS.

Webkit Bugzilla discussion referencing iOS 12, iPhone 5S
According to Apple's support pages, iOS 11 is compatible with the iPhone 5s, iPhone SE, and newer models. Support for the iPhone 5c and iPhone 5 wasn't included in last year's major release.
Even so, it is entirely possible for iPhone 5s support to be enabled for development and testing purposes, but not offered in the public release of iOS 12 when it ships later this year. References in one area are not a guarantee that Apple will definitely support specific hardware versions at a later time.
Due to open source software being visible to the public, WebKit is one of the more difficult areas for Apple to keep its future software plans out of view. Apple developers working on the Safari browser rendering engine and submitting code are advised to use macros to eliminate any leaks for future software, as indicated in another discussion about iOS 12 and macOS 10.14.
The macros are meant to prevent the public project from being a source of software leaks, but evidently the "TBA macros" are not always used.
Apple is expected to unveil iOS 12, along with milestone versions of its other operating systems and major updates to its other software, during the WWDC 2018 keynote address on June 4.

Listings in the bug-reporting section of the open source Webkit project page, discussing API tests for the software, includes a report from one developer in January showing an implementation of the testing suite could be run using Python. The report, spotted by MacGeneration, specifically mentions iOS 12 in multiple sections, as well as the iPhone 5s, including the confirmation "iPhone 5s running iOS 12."
Rather than an unreleased version of the operating system running on an actual iPhone 5s, the start of the report indicates this to be API tests running in a simulator, mimicking the iPhone 5s in software.
If genuine, this would indicate both that iOS 12 is being used in testing of important software, like Safari. It would also make this a sign that iPhone 5s users could still be able to use the next iteration of iOS.

Webkit Bugzilla discussion referencing iOS 12, iPhone 5S
According to Apple's support pages, iOS 11 is compatible with the iPhone 5s, iPhone SE, and newer models. Support for the iPhone 5c and iPhone 5 wasn't included in last year's major release.
Even so, it is entirely possible for iPhone 5s support to be enabled for development and testing purposes, but not offered in the public release of iOS 12 when it ships later this year. References in one area are not a guarantee that Apple will definitely support specific hardware versions at a later time.
Due to open source software being visible to the public, WebKit is one of the more difficult areas for Apple to keep its future software plans out of view. Apple developers working on the Safari browser rendering engine and submitting code are advised to use macros to eliminate any leaks for future software, as indicated in another discussion about iOS 12 and macOS 10.14.
The macros are meant to prevent the public project from being a source of software leaks, but evidently the "TBA macros" are not always used.
Apple is expected to unveil iOS 12, along with milestone versions of its other operating systems and major updates to its other software, during the WWDC 2018 keynote address on June 4.
Comments
iOS 14 iPhone 6S
iOS 15 iPhone 7
iOS 16 iPhone 8
A7 is the first 64-bit processor for iOS, any device with A7 or later could be supported for years more...look at what Macs are compatible with the latest macOS, they go back as many as 8-9 years.
This means that when developing a game, backwards compatibility is totally crazy, adding dev cost and compromises to the game beyond ‘graceful fallback’.
I hope Apple will become more aware of this problem.
Also I’m not sure if it’s good for consumers. Again it will get people over to ios12 because it auto updates and people will realize how slow their device has become. Downgrading most people won’t because they don’t know how to, essentially creating the perception of their device becoming too slow to handle and somewhat quietly, gently forcing users to upgrade to a new device.
Just support old devices and let people stay using an old iOS version! Keep supporting security updates within reason for these legacy devices.
Best option? Get people to a subscription model, and make that financially attractive. This helps recycling of old devices and gets people to new devices.
I was thinking the same thing. With all the talk of "planned obsolescence", it very obvious to anyone who knows Apple that they actually support products for a long time (and actually, that was the point of CPU throttling, to prolong battery life). The thinking behind this is that Apple makes all their money from selling hardware, but in apple's case this is flawed logic; it does not apply to a company that sells to the high end of the market, with high margins. Apple can afford to keep supporting their devices a lot longer than a company that is selling products with razor thin margins. Those companies need sales, a lot of them, to sustain themselves. Therefor, it is in their best interest to not support devices soon after they're sold, with the hopes that those consumers will by another in the near future.
My late 2009 iMac (Core i7) is still supported in the latest macOS release. However, I do fear its days are numbered. LOL Over the years, I've upgraded the memory, internal hard drive, replaced the internal DVD drive with an SSD, and upgraded the WiFi/Bluetooth module. I don't have plans to buy a new Mac anytime soon, but will probably buy a new iPad Pro (hopefully) this summer.