If you’re a fan of Pokémon GO and have an older iPhone that cannot run iOS 11, this might be the time to upgrade your phone. Niantic has just posted an update to their blog that they are discontinuing support for iPhones that cannot run the newest version of Apple’s operating system. This will happen on February 28, 2018. After that update, you will not be able to access your account at all. So if you want to continue, you must get a newer phone.
[Source: Niantic Labs Blog]