If we change the versioning system at all, our versions should converge against an irrational number as TeX does. Unfortunately, pi is taken and we are past e. Any suggestions? Inf? NaN?
If it was up to me I would consitently looseobvious the order of release 'numbers'. This way people would not consider moaning about it, just accept it as an eccentric fact of life. The truth is that the OSS development model naturally disambiguates any version numbering. In drupal's case the only hard meaning number is the third one - it is a bugfix release, no api changes. The rest is too vague, and you really need to dive into the development history, get PhDs in OSS archeology and psychology and form a theory. Which might reflect a portion of the truth. Drupal 5.x.x will probably come when it feels right, to whoever is around at the time. And that is the most precise definition. You will find various other explanations around that time as well, but the main reason will still be it looks like 5, feels like 5, so it is 5. It is duck versioning :)