You can already do this for wp-content. I think the next logical step for WP would be to allow the user to define a custom wp-admin path. Some users think this would make wp more secure. While I am not sure what I think about that I would like my admin path to be something more generic like admin. wp- everywhere just kinda annoys me. Granted most wp- files aren't accessed directly but are hidden by permalinks that’s great but since wp-admin is accessed directly I want to change it.
Also wp-signup.php and wp-login.php should optionally be able to be hidden via a permalink as well.