It runs in desktop web browsers on Windows, Mac and Linux (soon only hosted in Chrome, but it will be there). It runs on iOS, MacOS, Windows, Android and Blackberry with Adobe Air and it's far better, faster and easier to develop for than any Javascript/HTML5 alternative. If you want to get a clue about how is Flash doing lately, just browse Flash Daily from time to time.
It doesn't run on iOS , the version for android/blackberry is declared dead. Windows 8 will only support it in it's legacy "desktop" mode, it's shrinking to one browser under Linux and somehow I doubt Apple wants to keep in running under OS X for any longer than they have to.
Flash RUNS on iOS/Android/Blackberry, there are a lot of Flash apps on all those platforms, including best selling ones[1]. Adobe just discontinued the mobile version of the Flash browser plugin, but what you don't understand is that with the launch of Adobe Air, Flash is no longer tied to the browser plugin. It's kind of irrelevant what Apple pontificates next or what Microsoft decides to support themselves in Metro, Air apps written in Flash will continue to come to iOS, MacOS, Windows 8 etc because it's the best and easiest way to develop cross platform applications. JS/HTML5 is not even close in performance, capabilities, ease of development or consistency (I'd like to see someone do anything as cool as this[2] with JS/HTML5 on mobiles), the only thing that comes close to Air right now is .Net/Mono (with MonoTouch and MonoDroid).
[1] http://flashdaily.net