Soudan going independent in OTL was for the most part, the result of Nasser's policy who sought at all costs to eliminate all British/western presence from the arab world. Since the anglo-egyptian treaty on Soudan was the only thing that kept the British there, revoking it was a means of forcing the british out, at the cost of losing claims to Sudan by Egypt. It was a bargain possible due to two cicumstances - US pressure there for decolonization as fast as possible (as the US agenda at the time was ending colonial presence everywhere, so that pro-independence movements don't associate with communists) and the strong pan-arab movement (Nasser truly believing that after western withdrawal the road to the unification of arab states would be open, so "independent Soudan" would only be a temporary messure).
So having Nasser not annul the treaty would mean a viable Egyptian claim to the territory, British eventual withdrawal making it possible for Egypt to move in. It doesn't really have to be Nasser even - any Egyptian government, even the monarchical one could do that. Or you can have Nasser's dream of a pan-arab state with him as leader come true after a successful war against Israel, after which he could just Anchluss Sudan.