I've though about it more than once. Having the forum rules on the wiki would really make it a lot easier to edit, at least for me (the English and French topics are locked and as I'm no longer an admin nor a moderator, I have to ask a mod to unlock them to make changes, this is a hassle I find more and more difficult to live with).
It would also be much, much easier to keep the translations in sync with the original English one. Not only that, the translations would all be accessible from the English page.
What stopped me was that newcomers may get confused, because clicking on such a link would send them away from the forum. We would need to add some text like "to get back to the forum, click on the Back button of your browser".
On thing to remember, if we decide to do this, we should not delete the existing "IMPORTANT" topic, but simply strip it from its content and add a link to the wiki page; otherwise, the gazillion links we've pasted on the forum over the years would go dead.