I wish they'd abandon this rapid-release cycle and just go back to releasing revisions of releases, such as 3.1, 3.2, etc. They're just copying Chrome with the new version number every couple months nonsense.
Versions 4, 5, and 6 had no truly remarkable or massively significant changes. Really, they could all just be versions 4, 4.1, and 4.2. If version 7 does actually include a (much needed) major memory usage overhaul, then it would be the first one with a truly significant change, making it the only one that's truly worthy of a new version number.
Mozilla releases new version numbers just to keep up with the Joneses (er, Googleses?).