A poll commissioned by Peace Now (who we don't here from much these days) says that only 6% of the population of the settlements would illegally obey a decision from the political echelon regarding the dismantling of settlements. One third of these (ie. 2% of the total) would be prepared to use weapons to resist evacuation.

What would actually happen would depend a lot on the circumstances of the evacuation (ie. negotiated vs. unilateral etc.) But when Prof. Irwin Wall writes in the New York Review of Books that

The problem in Israel's case is that nobody is willing to deal with the potential opposition of the settlers on the West Bank to the dismantling of settlements that has to accompany any peace agreement, and that similarly threatens to pit Jews against Jews in an orgy of violence. The problem is all the more dangerous because it runs roughly along a fault line between religious and secular Jews in Israeli society.

.. you can know for sure that he is no clue at all what he is talking about.