To make it even less scary, how about:
:Unless you are [[Special:Userlogin|logged in]] your edit will be signed with your [[IP address]] when you click 'Save'. See our [[Wikipedia:Privacy policy|privacy policy]].
Having an edit be signed with your IP number is IMO less threatening than saying we'll show your IP number publically, more of a way of granting attribution for the contributor's fine work than a warning that "we're watching you!". This version does unfortunately omit the point that Wikipedia records the IP address of logged-in users too, but it's not like we can compress every detail of the privacy policy down into just two lines and it should be pretty obvious to anyone who's thinking about this sort of thing so hopefully not a major omission.
The thing is, this is factually incorrect. Your IP address *will* be recorded and associated with your edits if you are signed in, and this omits the fact that if you are not logged in, it will be associated with your edits publically. This is the key point of adding this message - to warn people that their IP address will be made public if they edit without being logged in. Omit this, and you may as well not have the warning.
Chris