Bush will not invade Iran this year because he doesn't have the troops to do it. The US is already over-streched in Iraq. Unless they bring back conscription, which they wont. It is that simple.
He might order some airstrikes, but probably wont since it will be far too much hassle for very little result.
And he wont order an invasion any time soon since he wont be in power for very long.
So that leaves Israel. Who are the most likely to launch a few airstrikes. But even then, this is not Osirik and Iraq. It wont be a case of launching one missile and that's that.
So, at teh moment, everyone is trying to find a peaceful resolution, because no one can afford a war: Neither the US, nor the EU (as if), neither Iran. So they will shuffle until they find some kind of arrangement whereby someone (Russia) offers them peaceful nuclear technology in exchange for inspectors that run around the country.
It will hold for a bit. But Iran wants nuclear technology, and they will get it eventually.
The snag is that Iran getting nukes would not be an "Islamic bomb" as those ignorant commentators put it. It would be a "Sunni bomb". Which is different, and which would not please the Arab world.
People seem to forget that the Middle-East isn't made of "Arabs". Iranaians are Persians. Most are Sunni. Most of the Iraqis are Shias, and those two groups hate each other. Hence the civil war in Iraq.
It's fascinating how the media can simplify everything, and turn it into a "Us agaisnt Them" scenario, when in fact it's so much more complicated than that.
Anyway, Bush won't order a war this summer. Duh.