The wait for the next step in the evolution of Firefox is almost over, and it has been quite a wait. In all fairness, with Firefox 3.6.4, Mozilla in not cooking just a minor update to its open source browser, but going for a more consistent refresh instead. Essentially, Firefox 3.6.4 has swallowed Firefox 3.7, with the browser maker motivating the move with the necessity to boost the stability of its product through the introduction of a new feature designed to cut off plug-ins from Firefox. According to Mozilla’s current plans, Firefox 3.6.4 is scheduled for release on June 1st, 2010, almost two months after the previous release, v3.6.3.

At the start of this week, Firefox 3.6.4 inched forward with a new Beta build offered for testing. Firefox 3.6.4 Beta Build 4 is currently up for grabs, but the update has at least one more hurdle ahead of being wrapped up. “Firefox 3.6.4 build #4 was built last week and went to existing 3.6.4 beta users on Friday [May 14]. We are releasing Firefox 3.6.4 build #4 to the rest of the beta audience [as of May 18], though we know it isn't final,” an excerpt from the transcript for a Mozilla meeting held yesterday reads.

Mozilla continues to work hard in order to resolve all the blockers that are preventing it from finalizing Firefox 3.6.4. As of May 18, there were six remaining blockers, only two of which had fixes. Tomorrow, Mozilla plans to generate Firefox 3.6.4 Beta Build 5, a release that it will ship to all Beta testers on May 24th. The plan is to have Firefox 3.6.4 finalized and served to the public as early as June 1st.

With Firefox 3.7, Mozilla intended to deliver Out of Process Plug-ins to users, a feature that has plug-ins such as Flash and Silverlight running separately from the browser. This means that, in the eventuality in which plug-ins are affected by poor performance or crashes, they will no longer be able to impact the overall Firefox experience in any way.

Firefox 3.6.4 Beta Build 4 is available for download here.

Firefox 3.6.3 for Windows is available for download here.
Firefox 3.6.3 for Mac OS X is available for download here.
Firefox 3.6.3 for Linux is available for download here.