Apple announced that they will make the beta version of iOS 9 available to developers today, and the public starting in July.
iOS 9 will support all devices that support iOS 8. These include the iPhone 4s, 5, 5c, 5s, and iPhone 6 and 6 Plus. iPads supported include the iPad 2, 3, and 4, as well as the iPad Air and iPad Air 2. The 5th-generation iPod Touch will also be supported. Some features, like iOS 9's new multitasking capabilities, will be limited to newer devices.