On this "Download Day" the developers want to set the Guinness World Record for Most Software Downloaded in 24 Hours. There won't be any further Release Candidates.
From next Tuesday on the Plug-ins, which are one of the core features of Firefox, will be released for Firefox 3. Currently some of the most popular Plug-ins aren't available for Firefox 3, yet.
Firefox 3 RC2: Not all the Plug-ins are available yet.