In the never-ending game of musical chairs, ABC announced Tuesday that Charlie Gibson will be the new solo anchor of World News Tonight.  He replaces the current anchor, Elizabeth Vargas,  who will soon be going on maternity leave and Bob Woodruff, who is still recovering from his injuries in Iraq.  Charlie will start his new evening gig this upcoming Monday while continuing his morning stint on Good Morning America through June.  Vargas will resume her 20/20 co-anchor duties upon her return.  No replacement has been named yet to fill the soon vacant seat between Diane Sawyer and Robin Roberts.