Sounds like the main story is that they're redefining what a major version number means a la Chrome.
Chrome's numbers are not in the same scale as FF and IE too, of course. Users can't tell the difference between Chrome 6 and 7 like one can distinguish FF 2 and 3, or IE 6 and 7. I wonder, though, if Google was just trying to catch IE in version number with Chrome and once it's at 10, they'll stop increasing it so rapidly.
Chrome's numbers are not in the same scale as FF and IE too, of course. Users can't tell the difference between Chrome 6 and 7 like one can distinguish FF 2 and 3, or IE 6 and 7. I wonder, though, if Google was just trying to catch IE in version number with Chrome and once it's at 10, they'll stop increasing it so rapidly.