I thought it was going to take a million years, but it looks like my pessimism was not entirely justified, as the beta is apparently already available for download! So I downloaded the new Flash 9 Beta plugin HERE. Then I just uninstalled the old flash 7 plugin and cp’d this one into /usr/lib/firefox/plugins, and now it works! Restart firefox and verify everthing is correctly installed by entering about:plugins in the Firefox address bar and checking the version number of the Flash plugin. It is still a beta version, so people are encouraged to try the plugin as much as they can and report any problems. For me everything seems to be working fine, it’s a big improvement on Flash 7!
Flash Player 9 Beta version available for GNU/Linux!