ISIS has nothing but enemies. If you thought bin Laden was the one true devil. Well, he was almost an angel compared to ISIS. ISIS is like bin Laden and Hitler combined. Both bin Laden and Hitler had tons of friends, believe it or not. To ISIS, all of humanity is their combined enemity. As far as I know, Israel is part of humanity. Thus, Israel is no less an enemy of ISIS than anyone else.
You know what I mean. In the grand scheme ISIL is not a serious threat to Israel in the sense that long-term ISIL can't remake the region to one in which they are the dominant power. Iran however stands to do just that after ISIL is defeated by Iraq and the Assad regime.
In the long-term the Iranian "Shia Crescent" is the main enemy to Israeli power in the region. Not a militia army that will permanently remain in total political isolation, have no serious economy or production capacity for military equipment at any point, and has no long-range missile capacity, no air-force, or ground forces capable of putting up a serious fight against the Israeli army.