Israel is not and will not be the target of Iran with any future nuclear capability. The Iranian government knows the doctrine of "MAD" would apply to them and, contrary to popular belief, the Mullahs do not have any desire to commit national or personal suicide. "Israel" is a political tool that Iran and her allies use very effectively. They will continue to cause death and chaos in Palestine because it serves their political purposes. When it comes to a nuclear option their goals are much loftier than destroying Israel, which they know cannot be done militarily even with nuclear weapons.
This issue is much bigger that just Israel. The Iranians have long desired to be a major player in the world politically and militarily and they believe that nuclear weapons will give them what they could never achieve otherwise. Through threats and coercion their aim is to control the world's oil supply. The nation who controls the flow of the world's oil controls, at least to a point, the world's commerce. That is real power and that is the power the Iranians are after. They could bring America and Europe to their knees by simply destroying the Saudi oil fields and seizing the fields in southern Iraq and Kuwait which would , effectively, give them control of about 85% of the world's oil supply. America is hardly in any position to stop them at this point. The only thing holding Iran back is they do not have the Nuclear weapons yet. If they are successful in their weapons program then they they will move. This is the real danger to the world if Iran succeeds in acquiring Nukes....the threatened "destruction of Israel" is a political ploy that is very effective.