The iPhone 4s IS supported under iOS 9 and later versions of iOS 9. My girlfriend's employer supplied iPhone 4s was upgraded to iOS 9.2 and works just fine. It is no speed demon like her personal iPhone 6, but its hardware is eight times slower than the iPhone 6's hardware and sixteen times slower than the iPhone 6S's hardware. It still works but it is hardly a brick.
This class action lawsuit, like the previous ones based on the same argument, will be tossed out for lack of evidence. The plaintiffs cannot prove their contention that Apple deliberately made iOS 9 to obsolete the iPhone 4s. . . because it still works on the iPhone 4s.
We shall see. Good to be objective if they are doing this good that it gets publicized.