I suspect that without American support, they would have to do quite a bit to change their behavior. They probably can't afford the current level of conflict on their own. It would force them to negotiate with their neighbors.
Iran[1] may also have all the pieces for nukes by then[2], hence Bibi's fraught gamble with the decapitation strikes, and present desperation to continue - even escalate - hostilities.
1. Or the UAE, which has shown interest in nuclear tech, perhaps for strictly peaceful purposes
2. I.e. attain nuclear latency, and finally make real what Netanyahu has been warning the world for decades: that Iran is "weeks away from a nuclear bomb"