It has been Bush & Cheney's intention to invade Iran since before they invaded Iraq. No one can say they didn't see it coming.
This is from a 2003 New Yorker article:
There is little doubt that some of the most hawkish ideologues in and around the Bush Administration entertain dreams of a kind of endless war. James Woolsey, a former director of Central Intelligence who has been proposed as a Minister of Information in Iraq by Donald Rumsfeld, forecasts a Fourth World War (the third, of course, having been the Cold War), which will last “considerably longer” than either of the first two. One senior British official dryly told Newsweek before the invasion, “Everyone wants to go to Baghdad. Real men want to go to Tehran.” And then, presumably, to Damascus, Beirut, Khartoum, Sanaa, Pyongyang. Richard Perle, one of the most influential advisers to the Pentagon, told an audience not long ago that, with a successful invasion of Iraq, “we could deliver a short message, a two-word message: ‘You’re next.’ ”
You can read the whole thing here:
War Without End