Right now, they are all there illegally and their thuggish attitudes are a stumbling block to peace. Very likely they would create a crisis in independent Palestine which would force/persuade Israel to intervene on their behalf. Also, many of them are living on land which has been stolen from Palestinian families. However, in the unlikely event that they vacated stolen land, gave up their privileges, and behaved as peaceful, law-abiding Palestinians, then they should be allowed to stay.
ISIS claims responsibility for attacks on Yemeni government HQ in Aden (Reuters)
from the article: It isn't for the state to promote Arab-Jewish coexistence