Windows 7: Firefox 4.0 Beta in mid-2010, Final in Late 2010.

If all goes according to plan, Mozilla might release no less than three versions of its open source browser in 2010, culminating with Firefox 4.0. The next major version of Firefox is scheduled for general availability by the end of 2010. Of course, this is nothing more than a preliminary estimate of the delivery deadline for Firefox 4.0, and an optimistic one at best. The fact of the matter is that, Firefox 4.0 could also slip into early 2011, which would leave just two releases of the browser in 2010, namely 3.6 and 3.7.

At the start of this week, the number of Firefox 3.6 Beta Testers was approximately 600,000, but expected to lower over the holidays. Mozilla shipped the fifth Beta build last week, introducing more than 130 fixes over Beta 4. Firefox 3.6 Beta 5 is currently available for download for early adopters. At the same time, the company is laboring to produce the first Release Candidate of Firefox 3.6. In this regard, testers could be getting their hands on Firefox 3.6 RC by year’s end, although this development milestone could also slip into 2010.