Although Mozilla hasn't even released the final version of Firefox 3.0, its developers are already hammering out plans for the next edition, which may come as soon as late 2008, according to posts written by company executives.

In a thread on the mozilla.dev.planning newsgroup, Mike Schroepfer, vice president of engineering for Mozilla, summarized the post-Firefox 3.0 plans that had been discussed. Among them: Firefox 3.1, which could appear around the end of the year.

"There were a number of features that we held back from Firefox 3 because they weren't quite ready, but they were nearly complete," said Schroepfer in a message that kicked off a relatively active thread on the newsgroup. Schroepfer cited several features that failed to make the Firefox 3.0 cut, including support for XMLHttpRequest (XHR), an API used by JavaScript and other browser scripting languages to transfer XML and other data between clients and servers.

Mozilla yanked XHR support from Firefox 3.0 before posting Release Candidate 1 (RC1); according to the RC1 release notes, it did so "until the specification becomes more stable and the security model is improved."

[ See related story: "Mozilla launches Firefox 3.0 RC1 early." ]

"...The overall quality of Gecko 1.9 as a basis for mobile and the desire to get new platform features out to web developers sooner has lead to us want to do a second release of Firefox this year," Schroepfer continued on the Mozilla newsgroup. "This release would be date-driven and targeted at the end of 2008."

The move would be a first for Mozilla, which has never rolled out two major versions of its flagship browser in the same calendar year.

After Firefox 3.1 the picture gets hazier, said Schroepfer. "Firefox 4 will incorporate some of the more aggressive platform improvements in Mozilla2," he said, referring to the already-underway rewrite of the browser's underlying code. "It is far too early to set a shipping date but an initial target would be sometime in late 2009," Schroepfer said.

He also reiterated Mozilla's now-standard support lifecycle plans for Firefox 2.0, the current production version. "Support releases for Firefox 2.0.0.x will terminate at the latest approximately 6 months after the shipment of Firefox 3," he said. This coincides with the approximate ship date of Firefox 3.1." As Schroepfer pointed out, Mozilla has committed to supporting older software for only six months after the release of a major update. A year ago, for example, it dropped support for Firefox 1.5 after it released that edition's final security update.

Mozilla published Firefox 3.0 RC1 for download last Friday, and is now trying to decide whether to call that version good enough or issue another release candidate to fix several lingering or newly uncovered bugs.

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