Mike Beltzner, Mozilla director of Firefox, said in a blog that another goal for Firefox 4 is empowering users to be in full control of their browser.
The plans, though, remain "fluid and are likely to change," Beltzner said.
"As with past releases, we use dates to set targets for milestones, and then we work together to track to those targets. We always judge each milestone release against our basic criteria of quality, performance, and usability, and we only ship when it's ready."
Plans call for performance optimisation and simplification, including fewer user interface controls. Users would be able to manage their relationships with websites via control over permissions.
Other improvements eyed include making it easier to find relevant add-ons and installing them without restart.
3D capabilities would be offered via WebGL, and animation of web content would be enabled via CSS Transitions and SMIL (Synchronised Multimedia Integration Language).
A beta release is expected to be made available in early-July, with plans to ship the browser by the end of this year.
Meanwhile, the planned Firefox 3.7 release has been rebranded as Firefox 3.6.4, with improvements for handling out-of-process plug-ins.
These plug-ins had been causing crashes. Version 3.6.4 is due this month.