Unfortunately, Mahmoud Ahmadinejad has repeatedly told that that there must be “cataclysmic events” to prepare the way for Shiite Muslims’ awaited messiah (The reappearance of the 12th Imam).
Also, several top-level iranians have openly told that Israel should be nuked. This includes one of the former “reformist” Iranian presidents in his speech in 2001.
I still agree with the idea of Israel increasing their deterrence level.
If the regime would be interested first and only in nuking Israel, they would have quietly finished their bomb and launched them without fanfare.
They aren't that stupid. If that would have been their goal, they wouldn't have blown the whistle so loud. Not only Taqqiya but also simple strategical thinking demands that.
The islamic rhetoric is bluster to impress the Muslim world and to assert that Iran is the only power to "liberate Palestine". The loud rhetoric also serves of testing the water of Western/Israeli determination. The mullahs must feel pretty reassured over the lame reaction.
They will build their bomb, or at least stop at the brink of being able to do so within a short time, to blackmail the world. They can demand high oil-prices, strategic concessions and be safe from attacks.
That way they will achieve their goals of being the regional dominant power, dominating Iraq, Syria and Lebanon and continue/increase their attacks on Israel through terrorist proxies.
If you think they will launch a nuke... don't hold your breath.
Now what I say doesn't mean that it's not a clear threat. It is! But not in the shape many apparently expect. The islamic regime being able to blackmail the world is bad enough.