It won't happen. However, how would it "bring more people to WEForums" if we're advertising other sites?
WEForums is big enough as it is. Being this big, we require money to be advertised on our site.
Also, advertising in signatures is much better. For one, most people wouldn't enter an advertising forum BUT to post their site (meaning threads would have few views, leading to very few actual clicks). Secondly, signatures are displayed after every post you create and are unavoidable for the most part (few people remove signatures through the usercp). Finally, the more posts you make, the more posts WEForums receives, and in turn for helping us, you help yourself.