Mozilla's new developmental roadmap reveals that Mozilla 1.4 will be made the new stable release to replace Mozilla 1.0. Mozilla 1.5 and forward will abandon the current Mozilla browser suite, instead implementing Phoenix and Minotaur, stand alone, leaner versions of Mozilla Navigator and Mozilla Mail.

So it looks like we might see a Netscape 8.0 in the fall, based upon Mozilla 1.4, with future release of Mozilla having a more modular design. MozillaZine has a reader-friendly post explaining these changes in more detail.