The latest Firefox Delivery meeting proposed Firefox 3.1, codename Shiretoko changed to Firefox 3.5. This is due to a lot of changes and improvement need to be done.
Here's some details.
"Under this proposal:
* Shiretoko would be released as Firefox 3.5,
* the upcoming third beta release would still carry the 3.1b3 version numbering,
* the following foruth beta will be numbered Firefox 3.5b4,
* “Minefield” builds from the trunk mozilla-central repository will be renumbered to 3.6a1pre until further notice - we will need to consider and decide on a version number for that release at a future date,
* the Gecko version numbering will not change, remain 1.9.1 on the mozilla-1.9.1 branch and 1.9.2 on the mozilla-central repository for the forseeable future."
Meanwhile, Mozilla has released Firefox 3.0.7 with security and stability enhancement.
Here's some details.
"Under this proposal:
* Shiretoko would be released as Firefox 3.5,
* the upcoming third beta release would still carry the 3.1b3 version numbering,
* the following foruth beta will be numbered Firefox 3.5b4,
* “Minefield” builds from the trunk mozilla-central repository will be renumbered to 3.6a1pre until further notice - we will need to consider and decide on a version number for that release at a future date,
* the Gecko version numbering will not change, remain 1.9.1 on the mozilla-1.9.1 branch and 1.9.2 on the mozilla-central repository for the forseeable future."
Meanwhile, Mozilla has released Firefox 3.0.7 with security and stability enhancement.