Thanks to supernova_00 for the heads up.
Ben Goodger has updated the Mozilla Firefox Roadmap with the latest information about the path to 1.0.
Development will remain on the AVIARY_1_0_20040515_BRANCH (itself cut from the Mozilla 1.7 branch) until 1.0, with three releases candidates planned. The launch of Mozilla Firefox 1.0 for Windows and Linux is currently scheduled for Tuesday 14th September. The Mac OS X version will be released a little later, following additional work to make Firefox fit in the Aqua look and feel.