With the news of the upcoming Firefox 3.6, comes hope that Firefox 3.5 is nearing completion. As of press, Firefox 3.5 is scheduled for a Beta 4 release on April 14th [as I am watching the Mozilla Project Weekly Status meeting live it has been announced the release date has been pushed back a week] which means we could see the final release may be as early as June (which would only be six months later than the original projected release date for then Firefox 3.1). Firefox 3.6 is code named Namoroka after the national park located in Madagascar. The main themes/goals for this build are desktop web apps and snappiness, but is likely to include many other features and improvements. See Namoroka feature plan drafts for more details. Some of the new features planned for this release are (from Mozilla Links):

Performance: get a perceivably better browser startup and tab creation times (reduced in at least 50ms), and improve overall responsiveness by adding animations for actions like tab creation, moving, bookmarking, etc.

A long time requested feature: theme and extensions activation without restarting is also planned for this release, at least partially.

Better user interface for file uploading.

Merge common site specific preferences with the site button.

An option to convert web apps into desktop web apps, which basically means bringing Mozilla Lab’s Prism into Firefox.

Use of Aero Glass so Windows Vista and 7 users finally get translucent toolbars.

At this time, Mozilla is giving a projected release date for Firefox 3.6 as May 2010. However, given the massive amount of new features there is a strong possibility it could be renumbered as Firefox 4 prior to release. Although doing so would be a major shift in development plans as Firefox 4 was going to be the first version to shift on to the Gecko 2.0 rendering engine from the current Gecko 1.9 version. So looks like Gecko 2.0 has been placed on hold for a bit and may be introduced in Firefox 5 sometime in 2011.