I may not have been as clear as I'd hoped. Incubation state and the choice of version number are independent factors. There are no rules regarding how version numbers are selected.
That a project is in incubation is basically a flag to an adopter that may be some heightened risk associated with adopting the code. A project is generally in incubation while:
1) The development team is still learning the Eclipse Development Process and IP Process; and/or
2) The project code itself is immature (e.g. unstable APIs, or just a lot of flux).
Both of these are pretty subjective, so I depend on the project team and PMC to make a determination regarding whether or not a project is ready. I tend to expect that a mature project has a well-defined build process, good contributor documentation, is engaging (or at least trying to engage) their community, etc., but--again--I tend to defer to the project team and PMC.
I generally like for a project to engage in at least one release review while in incubation (to learn the process and give me a chance to fill in any gaps in their knowledge). Very often, projects will do that one incubation release review and then combine a graduation review with their next release review.
Some projects seem to stay in incubation forever. Frankly, I need to stop letting this happen.
