It looks like Mozilla won't be able to deliver on its promise to release Firefox 3.6 by the end of the year after all. According to an update on the organization's Wiki, users of the beloved open-source browser can now expect to see version 3.6 released sometime in the first quarter of 2010, while Firefox 4.0, originally slated to ship late next year, could arrive as a beta in the summer of 2010 and in final form "in late 2010 or early 2011."

Code-named Namaroka, Firefox 3.6 is expected to deliver significant performance improvements, updates to the Awesome Bar, and integration with the Mozilla Labs Personas project to customize the browser's appearance. There's also a Firefox 3.7 in the mix, which will improve Windows start-up time and include the Jetpack system for easier to write, install, and upgrade plug-ins.

For version 4.0, Mozilla hopes to finalize a new feature called Electrolysis that will compartmentalize processes and tasks on a tab-by-tab basis — similar to Google Chrome — for improved stability. The next major Firefox release should also get significant user interface changes and users are invited to submit their own designs.

The delay might come as a disappointment to many loyal Firefox users, but will hopefully prove itself worthwhile when version 3.6, 3.7 and eventually 4.0 finally see the light of day. With Chrome getting extensions support, Microsoft stepping up development of Internet Explorer, and Opera continuing to work on improving JavaScript execution as well as introducing new features, competition is looking better than ever on the browser front.