On 10 February 2012, South Sudan became members of CAF (Confederation of African Football) during CAF's 34th Ordinary General Assembly in Libreville, Gabon. FIFA membership may soon follow at the FIFA Congress set to be held in Budapest (Hungary) in May.
However, FIFA are already preparing for South Sudan. Sometime in November/December 2011, the FIFA trigramme for Sudan was changed from SUD to SDN. Most likely SUD will be South Sudan's trigramme.
SDN on FIFA.com
SUD on FIFA.com
Couple of things to point out on the "SUD" page:
Last news date: 21 November 2011
Last ranking displayed: November 2011.
National league and association details - the same as "SDN".