I agree with you, Israelis have the means and the will. Only way they don't do it is if the US precipitates the change via the bomb or by enabling the revolution.
After Kerry attacked Bush for not doing enough to counter Iran, one may think a bold Bush would then feel vindicated in bombing Iran before the election, however, that is wishful thinking.
Again, diplomatic efforts will not work unless Iran immediately allowed U.S. inspectors into the country to seize all nuclear weapon development equipment, not likely.