Last week, we pointed out that the development of Firefox 4 was taking a lot longer than anticipated, as a result of which, the final version might not be released by the end of this year. A short while back, Firefox’s director Mike Beltzner, confirmed our fears in an update posted on Mozilla’s Dev Planning group. He wrote:

As those who have been tracking our nightly builds know, great things are happening with Firefox 4. The user interface changes are converging, the graphics and layout features are wrapping up, and recently the JavaScript engine was dramatically improved. The result is a fast, capable Firefox that provides better speed and responsiveness for web applications and users. Completing this work is taking longer than initial estimates indicated as we track down regressions and sources of instability. As part of our commitment to beta users, we will not ship software before it is ready.

Firefox 4 Beta 7, which was originally expected to arrive on Sept 17, will ship in early November. Similarly, the release date of Beta 8 has been pushed back from October 1 to Nov 12. The RC build (Release Candidate) should arrive in early 2011, which will be followed shortly thereafter by the final build.