According to President Omar al-Bashir, if Sudan splits,

The President of Sudan, Omar al-Bashir, has said the north of the country will reinforce its Islamic laws if South Sudan votes for independence in a referendum next month. [7] Mr. Bashir said if the country split, the Sudanese constitution would be changed. Arabic would be the only language, Islam the only religion and Sharia the only law.
    "I think the tone was the thing that would surprise some." Just a couple of days earlier, President Bashir put him in a considerate mode, and he’d certainly made comments reassuring southerners living in the north that they would be fine if the south became independent. This was totally the opposite. [8] He said that there would be no space effectively for cultural or ethnic diversity in the new constitution that would come in if the south did separate.