As for a preemptive attack, which I imagine you meant would be nuclear since they're already giving it all they've got with their non-nuclear attacks, it is already clear that Israel and USA don't have a way to stop Iran's faster missiles, and they would have no way to prevent Iran nuking Tel-Aviv and Haifa in return. At that point Israel would cease to exist as a state and as a society. They would never risk that. The entire decades-long war against the middle east by USA and Israel is fought for the benefit of Israel, not for its destruction.