The Jurists differed in regards to when Dar al-Islaam becomes Dar al-Kufr.
The Shaafi'i school of thought has said that Dar al-Islaam never becomes Dar al-Kufr under any circumstance even if the kuffaar gain superiority, evacuate the Muslims from of it, and their 'ahkaam become supreme.
The Maaliki and Hanaabilah say that Dar al-Islaam becomes Dar al-Islaam when the 'ahkaam of the disbelievers manifest in it.
Kuwaiti Encyclopedia of Fiqh
Volume 20 Page(s): 201-202