Justice Ginsburg is the only women on the court so it's safe to say that she would be replaced by a woman. Matt Cooper has a short list,
Among the possible female candidates the president could consider are Elena Kagan, the Harvard Law School dean who has been named to be solicitor general. Nancy Gertner, a district court judge in Massachusetts. If Obama's interested in returning to the historic tradition of appointing a politician to the bench, the possibilities include Jennifer Granholm, the governor of Michigan and a Harvard Law School graduate and former state attorney general. Janet Napolitano is the former attorney general and governor of Arizona and now Secretary of Homeland Security. Diane Wood is a federal judge in Chicago. Sonia Sotomayer, a federal judge in California, if named, would be the first Hispanic justice.