According to the latest Mozilla Platform meeting minutes, Firefox 3.6.4 beta will be available tomorrow for general testing.
In recent days, the Firefox 3.6 branch became Lorentz, the code name for the first Firefox release to feature out of process plugins, which aims to improve overall stability by running plugins like Adobe Flash, Silverlight, and Java in their own independent process.
The inclusion of a features such as out of process plugin (OOPP) in a maintenance release (.6.x), is a departure from Mozilla’s classic update model which would leave new features for major updates (like 3.7 for example). In fact, OOP was backported from Mozilla trunk, the code base of Firefox.next (nightly trunk builds are labeled 3.7 right now, also a first.
Firefox 3.6.4 final release is targeted for early May.