Screen shot 2011 02 07 at 2.10.42 PM Mozilla to deliver Firefox 4, 5, 6 and 7 this yearAccording to Softpedia, Mozilla plans to release 4 new versions of Firefox, its open source browser by the end of this year.

Since we’ve had Firefox 3 since June 17th, 2008, we’re left wondering, “What’s taking so long? And why wait nearly three years to push out another version, just to release 4 all in one short span of time?”

In a Mozilla’s Product Priorities draft document for 2011, Mike Beltzner, Director of Firefox writes, “Ship our new technology to users in smaller bundles, more frequently” adding that Mozilla needs to push “four technology shipment vehicles in 2011, including Firefox 4 and achieve a regular cadence for shipping.”

Goals for Firefox’s development in 2011 include a polished shiny UI and to make sure that there is no more than 50 milliseconds between any user interaction and feedback from the browser. Now that is foxy.

The features for each new “version” include: Firefox 5 with the Account Manager and F1 Simple Sharing add-ons becoming built-in features and it looks like Windows 7 64-bit will be officially supported too.

Firefox 6 will focus on the Web applications framework, JavaScript optimizations, and support for OS X 10.7. For Web apps, some missing pieces of CSS3 and HTML5 will be added to Gecko, its rendering engine.

Firefox 7’s feature list is less limned: Electrolysis (splitting everything into separate processes) and changes to XBL support are mentioned but not much else.

For a complete product roadmap, see Firefox’s Wiki page.