Namoroka will continue to improve on performance. However, the focus will be on the interface and the application itself; startup times, time to open a new tab, and user interface responsiveness. "Common user tasks should feel faster and more responsive," the roadmap reads. To me, Firefox has always felt a bit sluggish in this area, so I certainly welcome the effort.
Another area of focus will be personalisation and customisation. For instance, the roadmap speaks of lightweight themes, which do not require a restart to be applied; this could build on the Personas project. They also want to introduce lightweight add-ons, which do not require a Firefox restart. They also seem to be taking a good look at Chrome's empty tab features, as they are thinking about implementing simple navigational controls in empty tab pages.
Other areas of focus will be better web application support, task based navigation, and better system integration; after Chrome and Safari 4, Firefox wants a Windows theme that makes use of Aero. They also mention Windows 7 support, which hopefully means support for Windows 7's new taskbar features. On the Mac OS X side of things, they want to make use of Mac OS X's native dictionaries (finally!).
Namoroka is set to arrive somewhere in 2010.