It was only a matter of time for something like this to happen with Pokemon GO and I'm sure it'll be happening for Android in the near future as well.
Earlier this week Niantic made an official announcement in regards to no longer supporting iPhones that are unable to upgrade to iOS 11. The obvious reason for this is that iOS 11 has the AR (ARKit) support in which the previous versions of iOS did not support. The Android chopping block will most likely be right around the corner as they are working on their Augmented Reality support, so we'll be sure to have a list of axed devices for you once it's released.
Check out the official announcement below:
In an upcoming update to Pokémon GO, we will end support for Apple devices not capable of upgrading to iOS 11, such as iPhone 5 and iPhone 5c models. This change is a result of improvements to Pokémon GO that push the application beyond the capabilities of the operating systems on such devices. This change will take effect on 02/28/2018. After that date, Trainers using affected devices may no longer be able to access their Pokémon GO accounts from that device, or use their PokéCoins or other items in their Bags. They will need to switch to a supported device to continue playing Pokémon GO. You can see the full list of impacted devices and learn more by visiting our Help Center.
And here are the devices that Pokemon GO will no longer support:
But lets be honest here, the only iPhone users that this effects are the ones who say "My iPhone will last forever" and haven't upgraded their phone in the past decade. Okay okay, that was an exaggeration but I don't fault iPhone users for not wanting to upgrade their phone when they're happy with it and they don't have to want to buy 10 different adapters with the new iPhones.
Let us know if you're one of those who's been impacted by this decision by Niantic.