Here are some possible scenarios that could take place as the year progresses.
Bush will insist upon Iran's nuclear plans, furnish proof of their 'evil plans', insist on Iran's involvement with terrorism and start a war with Iran near the end of his presidential term.
With a war booming and the possibility of Iran literally attacking US on its own soil and with the war having the potential to go nuclear, gas prices will jump exponentially and other countries now severely burdened by oil prices, others may join with Iran and a potential WW3 could start.
A war with Iran could also be a potential cover up just to have a nuclear factory 'explode' or a nuke could be dropped on Iran. Because Iran has large reserves of oil under their soil the oil could be potentially contaminated with radiation and all the massive reserves under their land could now be unusable thus creating a world wide oil based recession.
All of this is also a potential way for Bush to pass some new bill to keep him in office past his two terms because of the world crisis he has caused. Thus our president becomes a war mongering dictator.
If this does not happen and McCain becomes president, he will try to pick up this exact same course minus the dictator part.
Of course, Bush could always start up a war with Iran or set things in motion for it to take place, leave office and screw the next president into a position of having to declare war.