The feature set for Firefox 3.0 is constantly being tweaked by the Mozilla Corporation. The major update to the second most popular web browser is due in the second half of 2007. The Firefox 3 Wiki has been updated to divide planned changes and additions into two categories. "Functional" refers to changes such as 'support for Microsoft Cardspace' or 'improve search, retrieval, and startup performance' while "not functional" refers to updates such as "improve usability of Add-On Manager" or "simpler print preview dialog."
Features that are currently mandatory to the upgrade include an overhaul of the bookmark system and new identity management tools. Mozilla earlier claimed that major enhancements would be available on a yearly basis. According to the Firefox 3.0 release plan, however, incremental updates are a possibility (meaning a Firefox 2.5). If you haven't already, you can test drive Firefox 3.0 Alpha 1, dubbed "Grand Paradiso".