Apple's iOS 7 introduced Jony Ive's redesigned flat interface and a slew of new features built around it. Then iOS 8 brought the Mac and the iPhone closer together with a bunch more feature additions, with more incremental updates on the way to add Watch into the mix. It looks like iOS 9 won't be packed to the gills with more new stuff, but will finally make sure all of it reliably works.
If recent anonymously sourced reports are to be believed, Google might begin forcing smartphone manufacturers to keep their Android systems up-to-date - otherwise Google will remove support for key Google apps.