In a recent blog post Adobe wrote:
We will no longer continue to develop Flash Player in the browser to work with new mobile device configurations.
HTML5 is now universally supported on major mobile devices, in some cases exclusively. This makes HTML5 the best solution for creating and deploying content in the browser across mobile platforms.
With mobile usage set to shortly surpass that of desktop, it is hard to see how website owners can continue to use Flash for any device.