The AU is rightly becoming more flexible. It recognises Sudan as exceptional. Its break-up does not threaten the rest of Africa. ~The Economist 
This is always very easy for others with nothing at stake to say. Sudan’s break-up doesn’t threaten the rest of Africa until it provides the precedent in other countries for similar independence movements. Kosovo was supposed to be exceptional, too, until recognition of its independence more or less directly led to the effective partition of Georgia. When the U.S. and other states recognized Kosovo, few believed that it could have an effect on South Ossetia and Abkhazia, but it did. How many countries will suffer from greater instability because self-determination prevailed in Sudan?
Once major powers start re-drawing borders to satisfy the demands of self-determination or other concerns, there is no obvious place to stop. Kosovo’s example isn’t supposed to have any effect on the situation in Karabakh, either, but why are the people in Karabakh and Armenia bound by this Western assumption? Supporters of the secession of South Sudan have to take into account the possibility that the success of the southern Sudanese in achieving independence will encourage other separatist and automomist movements in Africa and elsewhere. In many ways, African nation-states are among the most arbitrary, artificial creations in the entire world, but that doesn’t mean that splitting them up into equally artificial, less viable statelets will make things any better. Kosovo’s separation from Serbia and eventual independence empowered  a gang of criminals. Is there much reason to hope for better in South Sudan?