According to an article in the Sudan Tribune, the African Union (AU) is proposing that a referendum take place in October of 2013 in which the people of Abyei will decide to link themselves to South Sudan or to Sudan. The proposal includes provisions for the Misseriya and Ngok Dinka who cross the borders between the nations. The AU suggests a “soft border” which would allow relatively free travel across the national boundaries regardless of the outcome of the referendum.
The proposal includes a provision in which 20% of oil revenues produced in Abyei will be shared with South Kordofan. This makes sense solely with the anticipation that Abyei will become part of South Sudan causing a further loss of oil revenue for Sudan. This all said, it is unlikely that any agreement on Abyei can be achieved until the situation with rebel groups along the border is settled because the agreement on Abyei seems to be dependent upon an ability to allow a soft border to exist.