Mozilla provided further details on its new, ambitious roadmap. The company aims to deliver Firefox 5 by June 21, 2011, and Firefox 6 is expected to follow as soon as August 18, 2011. More info at TechSpot.
All changes to Firefox source code are initially integrated in the mozilla-central Mercurial repository. At scheduled intervals (typically 6 weeks), the changes are imported from mozilla-central to one of three other channels (larger features and projects are usually initially developed in other repositories which track mozilla-central). In addition to mozilla-central (currently referred to as nightly), there will also be firefox-experimental, firefox-beta, and Firefox (release), each backed by its own Mercurial repository. These names are currently placeholders and Mozilla may still change them.