Maybe it isn't clear, but the reason people is asking for Maemo 6 on their N900 is because the OS itself is perceived to be lacking in many areas, and they would rather have an official, Nokia launch of the new software, instead of waiting for the community to pick up the job (which may or may not happen quickly).

Consider also that Maemo is so far monolithic, if there is a bug in, let's say, Modest, so far you won't be able to install Maemo 6 Modest, you need the whole block of the OS. That's a situation that presented itself in Diablo and the whole "Fixed in Fremantle" issue.