upcoming changes to the Firefox release schedule. The most notable change is a shift away from feature-driven releases to a fixed six-week schedule-driven release pattern.
Instead of major releases every 12 to 18 months, Firefox will shift to a four-channel system, just like Google's Chrome browser. The nightly channel (mozilla-central) will remain in place, but the beta audience will be split into Experimental and Beta channels. The final channel will be a stable build (Firefox 4, Firefox 5, etc.)
Every six weeks, code will be shifted from one channel to the next. At week 6, code will move from mozilla-central to firefox-experimental; firefox-experimental will move to firefox-beta; and firefox-beta will move to Firefox, the stable channel. Around week 12 and 18 the same process will occur, and so on, until the end of time. This means that we could see a major Firefox release every six weeks, once the machine starts turning.