Like its brethren browsers Google Chrome and Internet Explorer 8, Firefox is moving toward separating tabs into system processes, increasing browsing stability and taking advantage of increasingly common multi-processor systems.
The wiki outline of the "Content Processes" project states that the browser UI itself, and every page opened in a tab, would be split into a separate running process, which would "provide better application UI responsiveness" and improve stability. In terms of how most Lifehacker-ish types use Firefox—with a good number of useful extensions—this could only be seen as good news, as extension-related slow-downs might be walled off from actual content.
When would this happen? The wiki outline suggests a seriously rough "bootstrap," with a non-Firefox browser operating the browser "chrome" (interface) and a single tab as separate processes, is scheduled by July 15 of this year. Phase II, "Parallel Improvements," would see further work on safely connecting the browser chrome to the content, and is roughly estimated for Nov. 1, 2009. Extensions, performance optimisation, and multi-process content aren't even on a rough roadmap yet, so don't expect a multi-process Firefox in 2009.
Mozilla Links suggests Firefox could perhaps speed up its multi-process adoption by borrowing frameworks from the open-source well from which Google Chrome draws, Chromium. But what do you think? Is a multi-process, potentially more stable and CPU-adapted (and Chrome-like) browser the next big thing you've wanted from Firefox, or are there other areas you'd like to see worked on? Contribute to the open-source discussion in the comments. Content Processes [MozillaWiki via Mozilla Links]