Explaining its decision, WhatsApp said: “While these mobile devices have been an important part of our story, they don’t offer the kind of capabilities we need to expand our app’s features in the future. This was a tough decision for us to make, but the right one in order to give people better ways to keep in touch with friends, family, and loved ones using WhatsApp.
“If you use one of these affected mobile devices, we recommend upgrading to a newer Android, iPhone, or Windows Phone to continue using WhatsApp.”
If you’re worried about losing access then luckily this latest change should only affect a small number of iPhones.