Yes, there are definitely a lot of things in the codex that need some updating. I agree with Andrea that better documentation is needed on the fact anyone can edit the codex and join the developer list. It is not hard to edit a wiki.

I find this as a problem for any place that allows people to edit, even in the wiki communities. I watch the WMF list (Wikimedia Foundation) and there are always threads about getting ideas to get people motivated to participate, but those die faster than flies. There are only so many people willing to regularly update (I know this as a staffer at the wiki FanHistory.com .)