Mozilla’s next big browser update is running a bit behind schedule.

Firefox 4′s estimated release date has officially been pushed back to early 2011. The browser’s release schedule, which is posted on a public wiki, has been updated to show some new dates: beta 7 in early November, then three more betas before the end of the year, with the release candidate due early next year.

We were originally expecting Firefox 4 to be finalized by now, in late October, when the schedule was first laid out several months ago. But Mozilla’s release dates are always moving targets, so we were expecting things to change. But not this much. Now, the wait for Firefox 4 looks like it could stretch out to three more months, which is sure to upset those eagerly awaiting an update.

The good news is that the current beta is very stable (at least in our testing) and has enough polish to make it safe for day-to-day use. If you’re feeling a little bit rock and roll, we’d recommend downloading the latest Firefox 4 beta. The new features like the updated user interface, expanded support for new standards like HTML5 and CSS 3, plus a much-improved JavaScript execution engine make it worth the very small risk of a crash.

See also:

• Firefox 4 Update Fixes Mac, Windows Bugs
• Mozilla Labs’ New ‘Prospector’ Hopes to Improve Firefox’s Awesome Bar
• Mozilla Shows Off Plans for an Open Web App Store