If he kept his seat we would still control the Senate 51-49. I don't think he would resign. I'm sure his buddies would give him some plum assignment. Does Mississippi have a Republican Governor? If so, and Lott resigns, I'm sure the Governor would replace him with a Republican Senator.
The thing that really pisses me off is the double standard. Byrd is a former KKK member and dropped the "N" bomb in March 2001-not a peep from anyone.