I'm not usually one for making predictions, but I'll go out on a limb here and forecast what I believe the most likely outcome of the voter revolt in Iran.
There's no question a huge number of Iranians are seriously pissed off at the current regime. But I don't think it's safe to assume that all those people are necessarily opposed to the structure of the current regime. Yes, it's probably a pretty safe bet that many of the younger crowd hope for a less autocratic, more secular government. But take a look at the guy they really wanted to win. Mir Hussein Mousavi is hardly a true reformer wishing to take Iran down a more liberal, secular path. The differences between him and Mahmoud Ahmadinejad are more ones of style than substance. The fact that Ayatollah Hossein Ali Montazeri has cast his lot with the protesters should be ample evidence that this is more of a power struggle within the mullahcracy than a true secular revolution.
So, without further ado, my prediction: An agreement will be reached among the Guardian Council and the Assembly of Experts (the theocrats who actually run things in Iran) and Mousavi will be installed in place of Ahmadinejad. The unrest will quiet down as the majority will have had their say, and the status quo in Iran will be maintained.
Update 28 September 2009: It would appear my prediction was thoroughly wrong on one count (that Mousavi would be installed) and more correct than I'd like on the other count (that the status quo would remain).